Bookmarks    
nPr and nCr    
Random Number    
SD Calculator    
Sample Size    
Percent Error    
Density    
Molarity    
Molar Mass    
Ohm's Law    
Watts to Amps    
Voltage Drop    
Long Division    
Mixed Numbers    
Rounding    
Nth Root    
Exponents    
Half-Life    
Polar Form    
De Moivre    
3D Distance    
Point to Line    
Cross Product    
Determinant    
Sin Cos Tan    
Triangle Area    
Scale Factor    
Sector Area    
Ellipse Area    
Cube Volume    
Box Volume    
Sphere Volume    
Cone Volume    
Pipe Volume    
Time Duration    
Time Card    
Present Value    
Future Value    
Churn Rate    
A/B Test Calc    
SEO Traffic    
Ideal Weight    
Fat Intake    
Child Height    
Golf Handicap    
Heat Index    
Wind Chill    
Dew Point    
Download Time    
kWh to Cost    
AC Size (BTU)    
Heating Costs    
LED Savings    
Trip Gas Cost    
Tire Size    
Solar Output    
Solar Payback    
Battery Size    
Wall Area    
Gravel Needed    
Mortar Mix    
Slope Grade    
Curtain Size    
Soil Needed    
Sod Needed    
Ramp Length    
Blind Size    
Drain Slope    
Board Feet    
Heat Loss    
Furniture Fit    
Moving Boxes    
Plywood Cuts    
Shelf Sag    
   Add
Probability and random number calculators
Independent Events
Independent Events
Two Events Solver
Two Events Solver
Repeated Trials
Repeated Trials
Bayes' Theorem
Bayes' Theorem
Expected Value
Expected Value
Binomial Distribution
Binomial Distribution
nPr and nCr
nPr and nCr
Circular Permutation
Circular Permutation
With Repetition
With Repetition
Random Number
Random Number
Averages and statistics calculators
Average Calculator
Average Calculator
Mean Median Mode
Mean Median Mode
SD Calculator
SD Calculator
Quartiles & IQR
Quartiles & IQR
Frequency Table
Frequency Table
Correlation (r)
Correlation (r)
Normal Probability
Normal Probability
Z-Score Calculator
Z-Score Calculator
Confidence Interval
Confidence Interval
Sample Size
Sample Size
Mark & Recapture
Mark & Recapture
P-Value Calculator
P-Value Calculator
Percentage and ratio calculators
Percentage Calc
Percentage Calc
Percent Change
Percent Change
Percent Difference
Percent Difference
Percent Error
Percent Error
Ratio Calculator
Ratio Calculator
Discount Calculator
Discount Calculator
Sales Tax Calculator
Sales Tax Calculator
Margin Calculator
Margin Calculator
Speed calculators
Speed Calculator
Speed Calculator
Density and concentration calculators
Density
Density
Molarity
Molarity
Molar Mass
Molar Mass
Physics and electricity calculators
Ohm's Law
Ohm's Law
Watts to Amps
Watts to Amps
Resistor Colors
Resistor Colors
Voltage Drop
Voltage Drop
Unit conversion calculators
Weight Converter
Weight Converter
Shoe Size Converter
Shoe Size Converter
Integer and signed number calculators
Long Division
Long Division
LCM Calculator
LCM Calculator
GCF Calculator
GCF Calculator
Integer Calculator
Integer Calculator
Prime Factorization
Prime Factorization
Diophantine Solver
Diophantine Solver
Modulo Calculator
Modulo Calculator
Factor Calculator
Factor Calculator
Roman Numerals
Roman Numerals
Fraction, decimal and rounding calculators
Fraction Calculator
Fraction Calculator
Mixed Numbers
Mixed Numbers
Simplify Fractions
Simplify Fractions
Fraction to Decimal
Fraction to Decimal
Decimal to Fraction
Decimal to Fraction
Rounding
Rounding
Equation and inequality calculators
Linear Equation
Linear Equation
Linear Systems
Linear Systems
Quadratic Formula
Quadratic Formula
Absolute Value
Absolute Value
Quadratic Inequality
Quadratic Inequality
Polynomial calculators
Binomial Theorem
Binomial Theorem
Square root and nth root calculators
Simplify Radicals
Simplify Radicals
Nth Root
Nth Root
Exponent and logarithm calculators
Exponents
Exponents
Log Calculator
Log Calculator
Number of Digits
Number of Digits
Scientific Notation
Scientific Notation
Sci. Notation Math
Sci. Notation Math
Half-Life
Half-Life
Complex number calculators
Complex Numbers
Complex Numbers
Polar Form
Polar Form
De Moivre
De Moivre
Function and graph calculators
Slope Calculator
Slope Calculator
Linear Function
Linear Function
Direct & Inverse Variation
Direct & Inverse Variation
y = ax² Calculator
y = ax² Calculator
Distance Formula
Distance Formula
3D Distance
3D Distance
Section Formula
Section Formula
Point to Line
Point to Line
Lat/Long Distance
Lat/Long Distance
Complete the Square
Complete the Square
Circle Equation
Circle Equation
Conic Sections
Conic Sections
Polar Coordinates
Polar Coordinates
Sequence calculators
Arithmetic Sequence
Arithmetic Sequence
Geometric Sequence
Geometric Sequence
Fibonacci Sequence
Fibonacci Sequence
Recurrence Relation
Recurrence Relation
Vector calculators
Vector Calculator
Vector Calculator
Cross Product
Cross Product
Matrix calculators
Matrix Calculator
Matrix Calculator
Determinant
Determinant
Inverse Matrix
Inverse Matrix
Plane geometry calculators
Sin Cos Tan
Sin Cos Tan
Degrees ⇔ Radians
Degrees ⇔ Radians
a sin θ + b cos θ
a sin θ + b cos θ
Triangle Solver
Triangle Solver
Triangle Area
Triangle Area
Right Triangle
Right Triangle
Pythagorean Theorem
Pythagorean Theorem
Polygon Angles
Polygon Angles
Scale Factor
Scale Factor
Parallel Lines
Parallel Lines
Rectangle Area
Rectangle Area
Parallelogram Area
Parallelogram Area
Trapezoid Area
Trapezoid Area
Circle Calculator
Circle Calculator
Sector Area
Sector Area
Inscribed Angle
Inscribed Angle
Ellipse Area
Ellipse Area
Solid geometry calculators
Cube Volume
Cube Volume
Cube Surface Area
Cube Surface Area
Box Volume
Box Volume
Box Surface Area
Box Surface Area
Cylinder Volume
Cylinder Volume
Cylinder Surface
Cylinder Surface
Sphere Volume
Sphere Volume
Sphere Surface
Sphere Surface
Spherical Cap Volume
Spherical Cap Volume
Cap Surface Area
Cap Surface Area
Ellipsoid Volume
Ellipsoid Volume
Ellipsoid Surface
Ellipsoid Surface
Pyramid Volume
Pyramid Volume
Pyramid Surface
Pyramid Surface
Cone Volume
Cone Volume
Cone Surface Area
Cone Surface Area
Frustum Volume
Frustum Volume
Frustum Surface Area
Frustum Surface Area
Pipe Volume
Pipe Volume
Capsule Volume
Capsule Volume
Capsule Surface Area
Capsule Surface Area
Date and time calculators
Age Calculator
Age Calculator
Days Between Dates
Days Between Dates
Date Calculator
Date Calculator
Hours From Now
Hours From Now
Day of the Week
Day of the Week
Time Calculator
Time Calculator
Time Zone Converter
Time Zone Converter
Hours Calculator
Hours Calculator
Time Duration
Time Duration
Time Card
Time Card
Finance and economics calculators
Compound Interest
Compound Interest
Simple Interest
Simple Interest
Interest Calculator
Interest Calculator
TVM Calculator
TVM Calculator
Present Value
Present Value
Future Value
Future Value
ROI Calculator
ROI Calculator
IRR Calculator
IRR Calculator
Payback Period
Payback Period
Average Return
Average Return
GDP Calculator
GDP Calculator
Web marketing and ad metric calculators
CTR Calculator
CTR Calculator
Conversion Rate
Conversion Rate
CPC, CPM & CPA
CPC, CPM & CPA
ROAS Calculator
ROAS Calculator
Break-Even CPA
Break-Even CPA
LTV Calculator
LTV Calculator
CAC Calculator
CAC Calculator
Churn Rate
Churn Rate
A/B Test Calc
A/B Test Calc
A/B Sample Size
A/B Sample Size
SEO Traffic
SEO Traffic
Break-Even Point
Break-Even Point
Markup vs. Margin
Markup vs. Margin
CAGR Calculator
CAGR Calculator
Health and fitness calculators
BMI Calculator
BMI Calculator
Sleep Calculator
Sleep Calculator
Calorie Calculator
Calorie Calculator
BMR Calculator
BMR Calculator
TDEE Calculator
TDEE Calculator
Ideal Weight
Ideal Weight
Body Fat Calculator
Body Fat Calculator
Lean Body Mass
Lean Body Mass
Calories Burned
Calories Burned
Protein Intake
Protein Intake
Macro Calculator
Macro Calculator
Carb Calculator
Carb Calculator
Fat Intake
Fat Intake
Child Height
Child Height
Sports calculators
Golf Handicap
Golf Handicap
Pace Calculator
Pace Calculator
1RM Calculator
1RM Calculator
Target Heart Rate
Target Heart Rate
Weather calculators
Heat Index
Heat Index
Wind Chill
Wind Chill
Dew Point
Dew Point
Computer calculators
Base Converter
Base Converter
Subnet Calculator
Subnet Calculator
Download Time
Download Time
Household energy and budget calculators
Electricity Cost
Electricity Cost
kWh to Cost
kWh to Cost
Yearly kWh to Cost
Yearly kWh to Cost
AC Size (BTU)
AC Size (BTU)
AC Running Cost
AC Running Cost
Heating Costs
Heating Costs
Gas vs Electric
Gas vs Electric
LED Savings
LED Savings
Salary Calculator
Salary Calculator
Budget Calculator
Budget Calculator
Car calculators
Trip Gas Cost
Trip Gas Cost
EV Charging Cost
EV Charging Cost
EV vs Gas Cost
EV vs Gas Cost
MPG Calculator
MPG Calculator
Tire Size
Tire Size
Solar power and battery calculators
Solar Output
Solar Output
Solar Panel Count
Solar Panel Count
Solar Payback
Solar Payback
Battery Size
Battery Size
Home and DIY calculators
Tile Calculator
Tile Calculator
Stair Calculator
Stair Calculator
Concrete Volume
Concrete Volume
Wall Area
Wall Area
Wallpaper Rolls
Wallpaper Rolls
Paint Calculator
Paint Calculator
Flooring Needed
Flooring Needed
Exterior Walls
Exterior Walls
Gravel Needed
Gravel Needed
Mortar Mix
Mortar Mix
Slope Grade
Slope Grade
Lumber Cut List
Lumber Cut List
Lot Coverage/FAR
Lot Coverage/FAR
Sheet Vinyl Roll
Sheet Vinyl Roll
Insulation Needed
Insulation Needed
Curtain Size
Curtain Size
TV Size & Distance
TV Size & Distance
Soil Needed
Soil Needed
Sod Needed
Sod Needed
Block Calculator
Block Calculator
Brick Calculator
Brick Calculator
Deck Materials
Deck Materials
Ramp Length
Ramp Length
Pilot Hole Size
Pilot Hole Size
Room Ventilation
Room Ventilation
Paint Thinning
Paint Thinning
Baseboard & Trim
Baseboard & Trim
Blind Size
Blind Size
Picture Hanging
Picture Hanging
Drain Slope
Drain Slope
Screw Calculator
Screw Calculator
Board Feet
Board Feet
Fence Calculator
Fence Calculator
Wood Shrinkage
Wood Shrinkage
Caulk Calculator
Caulk Calculator
Heat Loss
Heat Loss
Furniture Fit
Furniture Fit
Moving Boxes
Moving Boxes
Storage Capacity
Storage Capacity
Plywood Cuts
Plywood Cuts
Shelf Sag
Shelf Sag

Quadratic Function y = ax² Calculator (Range for a Given Domain and Average Rate of Change)

Enter the coefficient a and choose what to calculate (the mode). For the range of y or the average rate of change, enter the x-interval p and q. For the value of y, enter a value of x.

You can use decimals, negative numbers and fractions such as 1/2. The fields change automatically to match the mode.
Result and graph
Enter the coefficient a and the x-interval (or a value of x) in the fields on the left and press "Calculate". The result and the graph will appear here.

What you can do on this page

  • For the quadratic function \(y = ax^{2}\), find the range of y for a domain of x, \(p \le x \le q\). The steps also explain the two cases, whether or not the domain includes 0 (when it does, the minimum or maximum is 0 at the vertex)
  • Find the average rate of change as x goes from \(p\) to \(q\), both by the definition \(\dfrac{\Delta y}{\Delta x}\) (change in y ÷ change in x), with steps, and by the shortcut formula \(a(p+q)\)
  • Find the value of y for a value of x (a point on the graph)
  • The coefficient a can be a whole number, a decimal or a fraction such as 1/2
  • The parabola is graphed. In range mode, the part for the domain and the range of y are highlighted; in rate-of-change mode, the line through the two points is drawn. A plain-language explanation of the formulas and copy-and-paste formulas for Excel, Google Sheets and Python are also on this page
This page covers \(y = ax^{2}\), whose vertex is at the origin. For the vertex and the maximum or minimum of the general form \(y = ax^{2} + bx + c\), use the related page "Completing the Square Calculator".

What is this calculation used for?

The path of a thrown ball

If you ignore air resistance, a ball thrown at an angle follows a parabola (the graph of \(y = ax^{2}\), shifted to another place).
A fly ball in baseball, a basketball shot and the water from a fountain all follow this shape, and this function is used to simulate sports and to move balls in video games.

A falling object's distance varies with the square of time (free fall)

If you ignore air resistance, the distance a dropped object falls is directly proportional to the square of the time since it was let go. With distance in feet and time in seconds, the constant is about 16, giving the quadratic function \(y = 16x^{2}\).
About 16 feet in 1 second, about 64 feet in 2 seconds: doubling the time makes the distance four times as large. This law, discovered by Galileo, is the starting point for the motion calculations in physics.

A car's braking distance grows with the square of its speed (road safety)

The distance a car travels from the moment the brakes are applied until it stops (the braking distance) is known to be roughly proportional to the square of its speed. Double the speed, and the braking distance becomes about four times as long.
This square relationship is the mathematical reason why speeding is dangerous. It is taught in driver's education, and it is a use of this function that directly affects safety.

Satellite dishes and reflectors (gathering radio waves or light at one point)

The shape you get by spinning a parabola around its axis (a paraboloid) has a special property: radio waves or light coming in parallel to the axis all meet at one point, the focus.
Satellite TV dishes and radio telescopes use this to collect weak radio waves. Flashlights and car headlights use it the other way around, to send light out in a straight beam.

Wind force grows with the square of wind speed (storms and buildings)

The force of the wind pushing on an object (wind pressure) is roughly proportional to the square of the wind speed. Double the wind speed, and the force becomes about four times as strong. This is why damage rises so quickly when a hurricane's winds get just a little faster.
When designing buildings and bridges, engineers use this square relationship to estimate the wind pressure from the expected wind speed, and decide how strong the structure must be.

Formulas and graphs

The quadratic function \(y = ax^{2}\)
Graph
Standard notation (the usual math form)
In words (symbols replaced with words)
\(y\) \(=\) \(a\) \(\times\) \(x^{2}\)
③ value of \(y\) \(=\) ② \(a\): coefficient \(\times\) ① \(x^{2}\): \(x\) squared
The formula in words
① Take \(x^{2}\): the value of \(x\) squared
② multiply it by the \(a\): coefficient
③ and you get the value of \(y\)
Quick example
For \(y = 2x^{2}\), the value of \(y\) when \(x = 3\) is
value of \(y\) \(=\) coefficient (2) \(\times\) 3 squared (9)
\(y = 2 \times 3^{2} = 2 \times 9 = 18\)
Key idea
\(y = ax^{2}\) is a function where "y varies directly with the square of x". It is direct variation \(y = ax\) with \(x\) replaced by \(x^{2}\), so \(a\) can also be called the constant of variation. The graph is a smooth curve (a parabola) with its vertex at the origin (0, 0). If \(a > 0\), it opens upward; if \(a < 0\), it opens downward. The larger the absolute value of \(a\), the narrower (steeper) the parabola. When you calculate, remember the order: square first, then multiply. To square a negative number, put it in parentheses, as in \(\left(-3\right)^{2} = 9\).
Range of y (when the domain includes \(0\), \(a > 0\))
Graph
Standard notation (the usual math form)
\(0\) \(\le\) \(y\) \(\le\) \(am^{2}\)
In words (symbols replaced with words)
② \(0\): \(y\)-coordinate of the vertex (minimum) \(\le\) ③ \(y\): values of \(y\) over the domain \(\le\) ① \(am^{2}\): value at the end \(m\) farther from \(0\) (maximum)
The formula in words
① Let \(m\) be whichever end of the domain, \(p\) or \(q\), is farther from \(0\) (the one with the larger absolute value). The maximum is the \(am^{2}\): value at the end \(m\) farther from \(0\)
② the minimum is not an end value but the \(0\): \(y\)-coordinate of the vertex
③ so the \(y\): values of \(y\) over the domain are greater than or equal to \(0\) and less than or equal to \(am^{2}\)
Quick example
For \(y = x^{2}\) with the domain \(-1 \le x \le 2\) (the end farther from \(0\) is \(m = 2\))
\(y\)-coordinate of the vertex (0) \(\le\) value of \(y\) \(\le\) value at \(x = 2\) (4)
\(x = -1 \Rightarrow y = 1, \quad x = 0 \Rightarrow y = 0, \quad x = 2 \Rightarrow y = 4\)
\(0 \le y \le 4\)
Key idea
Do not find the range of y just by substituting the end values of x. The right way is to picture the part of the parabola for the domain (the part where \(p \le x \le q\)) and read off its lowest and highest values of y. When the domain includes \(x = 0\) (the vertex), the graph comes down to the vertex (0, 0) and turns back up, so the minimum is \(0\), not an end value. With the example domain \(-1 \le x \le 2\), a classic mistake is to look only at the end values \(1\) and \(4\) and answer "\(1 \le y \le 4\)". When the domain does not include \(0\), the graph only increases or only decreases on that interval, so the end values are the minimum and the maximum. When the two ends of the domain have the same absolute value (for example, \(-2 \le x \le 2\)), \(am^{2}\) is the same at both ends, so the maximum is reached at both ends, \(x = \pm 2\). When \(a < 0\) (the parabola opens downward), everything flips: the maximum is \(0\) at the vertex, and the minimum is \(am^{2}\).
Average rate of change (as \(x\) goes from \(p\) to \(q\))
Graph
Standard notation (the usual math form)
\(\dfrac{\Delta y}{\Delta x}\) \(=\) \(aq^{2} - ap^{2}\) \(\div\) \(q - p\)
In words (symbols replaced with words)
③ average rate of change \(=\) ① \(\Delta y\): change in \(y\) (ending \(y\) − starting \(y\)) \(\div\) ② \(\Delta x\): change in \(x\) (ending \(x\) − starting \(x\))
The formula in words
① Take the \(\Delta y\): change in \(y\) (the ending \(y\) minus the starting \(y\))
② divide it by the \(\Delta x\): change in \(x\) (the ending \(x\) minus the starting \(x\))
③ and you get the average rate of change
Quick example
For \(y = 2x^{2}\) as x goes from \(1\) to \(3\) (\(y\) goes from \(2\) to \(18\))
average rate of change \(=\) change in y (18 − 2 = 16) \(\div\) change in x (3 − 1 = 2)
\(\dfrac{\Delta y}{\Delta x} = \dfrac{18 - 2}{3 - 1} = \dfrac{16}{2} = 8\)
Key idea
You find the average rate of change the same way as for a linear function: change in y ÷ change in x. But there is one big difference. The rate of change of a linear function \(y = ax + b\) is the slope \(a\) wherever you measure it, while the average rate of change of \(y = ax^{2}\) is not constant: it depends on where x starts and where it ends. On the graph, the average rate of change is the slope of the straight line through the two points (a secant line). A parabola is a curve whose steepness changes from place to place, so when the two points change, the slope of the line changes too.
Shortcut formula for the average rate of change of \(y = ax^{2}\): \(a(p+q)\)
Standard notation (the usual math form)
In words (symbols replaced with words)
\(\dfrac{\Delta y}{\Delta x}\) \(=\) \(a\) \(\times\) \((p + q)\)
③ average rate of change \(=\) ② \(a\): coefficient \(\times\) ① \(p + q\): starting \(x\) + ending \(x\)
The formula in words
① Take \(p + q\): the starting \(x\) plus the ending \(x\)
② multiply it by the \(a\): coefficient
③ and you get the average rate of change
Quick example
For \(y = 2x^{2}\) as x goes from \(1\) to \(3\)
average rate of change \(=\) coefficient (2) \(\times\) sum of 1 and 3 (4)
\(2 \times (1 + 3) = 2 \times 4 = 8\)
Key idea
This formula is a shortcut that works only for \(y = ax^{2}\) (vertex at the origin). The change in y, \(aq^{2} - ap^{2}\), factors as \(a(q + p)(q - p)\), so dividing by the change in x, \(q - p\), leaves just \(a(p + q)\). Calculating from the definition (\(\Delta y \div \Delta x\)) always gives the same value. It is a good idea to learn the meaning through the definition first, and use the shortcut to check your work or save time. For the general form \(y = ax^{2} + bx + c\), the shortcut becomes \(a(p+q)+b\).
The graph of the quadratic function \(y = ax^{2}\) is a parabola with its vertex at the origin (0, 0). Do not find the range of y from the end values alone; look at the part of the graph for the domain. When the domain includes \(x = 0\), the minimum (the maximum if \(a < 0\)) is \(0\) at the vertex. Unlike a linear function, the average rate of change is not constant; as \(x\) goes from \(p\) to \(q\), it equals \(a(p+q)\).

Symbols and terms

Symbols

\(a\) a The coefficient: the number multiplying \(x^{2}\). It decides which way the graph opens (up if \(a > 0\), down if \(a < 0\)) and how narrow it is. By custom, letters near the start of the alphabet, \(a,\ b,\ c\), stand for fixed numbers.
\(x,\ y\) ex, why Variables: letters for numbers that can take many values. By custom, letters near the end of the alphabet, \(x,\ y,\ z\), stand for unknown or changing numbers. On this page, choosing \(x\) determines \(y\).
\(p,\ q\) pee, cue The two ends of the x-interval: the left and right ends of the domain in range mode, and the starting and ending values of x in rate-of-change mode. On this page, \(p < q\) always (p is the smaller one).
\(m\) em A letter used on this page to explain the range: whichever end of the domain, \(p\) or \(q\), is farther from \(0\) (the one with the larger absolute value). The maximum (the minimum if \(a < 0\)) is reached at this end. When the two ends have the same absolute value, both ends give the same value.
\(\Delta x,\ \Delta y\) delta x, delta y The change in x and the change in y. \(\Delta\) (delta) is the Greek letter for D, the first letter of "difference", and it stands for "value after the change − value before".
\(\le\) is less than or equal to An inequality sign that includes the end value. \(-1 \le x \le 3\) says "x is greater than or equal to −1 and less than or equal to 3", so both −1 and 3 are included. Some countries write it with two lines, \(\leqq\), with the same meaning.
\(x^{2}\) x squared \(x\) multiplied by itself (\(x^{2} = x \times x\)). The small 2 at the upper right (the exponent) tells how many times \(x\) is used as a factor. To square a negative number, use parentheses, as in \(\left(-3\right)^{2} = 9\).

Terms

function When each value of x gives exactly one value of y, we say "y is a function of x". \(y = ax^{2}\) is a function too: choose x, and exactly one y is determined.
quadratic function A function where y is given by a degree-2 expression in x. The simplest form is \(y = ax^{2}\), with its vertex at the origin; the general form \(y = ax^{2} + bx + c\) lets the vertex move away from the origin.
coefficient The number multiplying a variable, such as the \(a\) in \(y = ax^{2}\). Because \(y = ax^{2}\) says "y varies directly with the square of x", this \(a\) is also called the constant of variation, just as in direct variation \(y = ax\).
parabola The smooth, symmetric curve that is the graph of \(y = ax^{2}\). It has the same shape as the path of an object thrown at an angle.
vertex The turning point of a parabola. The vertex of \(y = ax^{2}\) is the origin (0, 0); it is the lowest point of the graph if \(a > 0\) and the highest point if \(a < 0\).
origin The center of the coordinate plane, the point (0, 0), where the x-axis and the y-axis cross. It is labeled \(O\), the first letter of "origin".
domain and range The set of values a variable can take, written with inequalities such as \(-1 \le x \le 3\). The domain is the set of values of x; the range is the set of values y takes over that domain.
average rate of change The change in y divided by the change in x (\(\Delta y \div \Delta x\)). It tells how much y increases, on average, each time x increases by 1. It is constant for a linear function (the slope a), but for a quadratic function it depends on the interval.
change in x, change in y The amount of change, found as "value after − value before". If the value goes down, the change is negative (for example, going from 18 to 2 is a change of −16).
opens upward When \(a > 0\), the parabola has a valley shape. This is also called concave up.
opens downward When \(a < 0\), the parabola has a hill shape. This is also called concave down.
linear function A function of the form \(y = ax + b\) (its graph is a straight line). Its biggest difference from a quadratic function is that its rate of change is the same everywhere.

Good to know before you start

Here is what helps you use the calculation on this page with real understanding, not just by pressing the button.
If you get stuck, going back over these topics is the fastest way forward.

Positive and negative numbers (Grade 7)
  • Knowing that the square of a negative number is positive (\(\left(-3\right)^{2} = 9\)), and how this differs from \(-3^{2} = -9\) (only the 3 after the sign is squared)
  • Being able to subtract with negative numbers (for example, \(3 - (-1) = 4\))
Direct variation (Grade 7)
  • Knowing the form of direct variation \(y = ax\) and what the constant \(a\) stands for
  • Being comfortable with the idea of a function: choose x, and exactly one y is determined
Coordinates and graphs (Grades 6–7)
  • Being able to plot a point such as \((2,\ 8)\) on the coordinate plane
  • Knowing that a graph is a picture of all the pairs of x and y that make the equation true, drawn as points
Inequalities and intervals (Grades 6–8)
  • Being able to read \(-1 \le x \le 3\) as "x is between −1 and 3, including −1 and 3"
Linear functions and rate of change (Grade 8)
  • Knowing that the rate of change of a linear function \(y = ax + b\) (the slope \(a\)) is the same wherever you measure it
  • Knowing that the rate of change is found as (change in y) ÷ (change in x)

How to calculate it in Excel

Copy the whole table below and paste it into cell A1 in Excel. It works as is.
Table to find the range of y for a domain of x
Coefficient a 2
Left end of the domain p -1
Right end of the domain q 3
y at the left end =B1*B2^2
y at the right end =B1*B3^2
Minimum of y =IF(AND(B2<=0,B3>=0),MIN(0,B4,B5),MIN(B4,B5))
Maximum of y =IF(AND(B2<=0,B3>=0),MAX(0,B4,B5),MAX(B4,B5))
Table to find the average rate of change
Coefficient a 2
Starting x (p) 1
Ending x (q) 3
Starting y =B1*B2^2
Ending y =B1*B3^2
Average rate of change (Δy÷Δx) =(B5-B4)/(B3-B2)
Check with a(p+q) =B1*(B2+B3)
Table to find y for a value of x
Coefficient a 2
Value of x 3
Value of y =B1*B2^2
After pasting, the upper rows (the coefficient and the x-interval) are your inputs, and the lower rows are calculated automatically. "^" raises to a power (^2 is squared), and "*" is multiplication.
The first table is y = 2x² with −1 ≤ x ≤ 3. The values of y at the left and right ends are 2 and 18, and the minimum 0 and maximum 18 are found (the range of y is 0 ≤ y ≤ 18). The IF(AND(B2<=0,B3>=0), …) part checks whether the domain includes 0; when it does, the 0 at the vertex is also a candidate for the minimum or maximum. It works as is when a is negative.
The second table is y = 2x² as x goes from 1 to 3. The definition cell (Δy÷Δx) and the shortcut cell a(p+q) both give 8.
The third table substitutes x = 3 into y = 2x², giving 18.

How to calculate it in Google Sheets

Copy the whole table below and paste it into cell A1 in Google Sheets. It works as is.
Table to find the range of y for a domain of x
Coefficient a 2
Left end of the domain p -1
Right end of the domain q 3
y at the left end =B1*B2^2
y at the right end =B1*B3^2
Minimum of y =IF(AND(B2<=0,B3>=0),MIN(0,B4,B5),MIN(B4,B5))
Maximum of y =IF(AND(B2<=0,B3>=0),MAX(0,B4,B5),MAX(B4,B5))
Table to find the average rate of change
Coefficient a 2
Starting x (p) 1
Ending x (q) 3
Starting y =B1*B2^2
Ending y =B1*B3^2
Average rate of change (Δy÷Δx) =(B5-B4)/(B3-B2)
Check with a(p+q) =B1*(B2+B3)
Table to find y for a value of x
Coefficient a 2
Value of x 3
Value of y =B1*B2^2
The same formulas as in Excel work as is. Copy the whole table, paste it into cell A1, and replace the coefficient and the x-interval with your own numbers.

How to calculate it in Python

from fractions import Fraction

coefficient_a = Fraction(2)   # coefficient a (a fraction such as 1/2 can be written Fraction(1, 2))
left_end = Fraction(-1)       # left end of the domain p (for the rate of change, the starting x)
right_end = Fraction(3)       # right end of the domain q (for the rate of change, the ending x)

y_left = coefficient_a * left_end ** 2
y_right = coefficient_a * right_end ** 2

# Range of y: split into cases by whether the domain includes 0 (the vertex)
if left_end <= 0 <= right_end:
    candidates = [Fraction(0), y_left, y_right]
else:
    candidates = [y_left, y_right]
y_min = min(candidates)
y_max = max(candidates)
print(f"Range of y: {y_min} <= y <= {y_max}")

# Average rate of change (as x goes from p to q)
rate = (y_right - y_left) / (right_end - left_end)
print(f"Average rate of change (definition Δy÷Δx): {rate}")
print(f"Average rate of change (shortcut a(p+q)): {coefficient_a * (left_end + right_end)}")
The fractions module in the standard library lets you calculate with exact fractions, with no decimal rounding errors. This example is y = 2x² with the domain −1 ≤ x ≤ 3. When you run it, it shows the range of y, "0 <= y <= 18", and the average rate of change as x goes from −1 to 3, "4" (the same value by the definition and by the shortcut). Change the coefficient and the interval, and run it again.

How to write it in LaTeX and other math languages (copy and paste)

The quadratic function \(y = ax^{2}\)
y = ax²
y = ax^{2}
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mi>y</mi>
    <mo>=</mo>
    <mi>a</mi>
    <msup><mi>x</mi><mn>2</mn></msup>
  </mrow>
</math>
y = a x^2
a x^2
y := a*x^2;
y = a*x^2;
y = ax^2
Range of y (when the domain includes \(0\), \(a > 0\))
0 ≤ y ≤ am²
0 \le y \le am^{2}
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mn>0</mn>
    <mo>&#x2264;</mo>
    <mi>y</mi>
    <mo>&#x2264;</mo>
    <mi>a</mi>
    <msup><mi>m</mi><mn>2</mn></msup>
  </mrow>
</math>
0 <= y <= a m^2
{MinValue[{a x^2, p <= x <= q}, x], MaxValue[{a x^2, p <= x <= q}, x]}
minimize(a*x^2, x = p .. q); maximize(a*x^2, x = p .. q);
m = max(abs(p), abs(q)); ymin = 0; ymax = a*m^2;
0 ≤ y ≤ am^2
Average rate of change (as \(x\) goes from \(p\) to \(q\))
Δy/Δx = (aq² − ap²)/(q − p)
\dfrac{\Delta y}{\Delta x} = \dfrac{aq^{2} - ap^{2}}{q - p}
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mfrac>
      <mrow><mi>&#x394;</mi><mi>y</mi></mrow>
      <mrow><mi>&#x394;</mi><mi>x</mi></mrow>
    </mfrac>
    <mo>=</mo>
    <mfrac>
      <mrow>
        <mi>a</mi><msup><mi>q</mi><mn>2</mn></msup>
        <mo>&#x2212;</mo>
        <mi>a</mi><msup><mi>p</mi><mn>2</mn></msup>
      </mrow>
      <mrow><mi>q</mi><mo>&#x2212;</mo><mi>p</mi></mrow>
    </mfrac>
  </mrow>
</math>
(Delta y)/(Delta x) = (a q^2 - a p^2)/(q - p)
(a q^2 - a p^2)/(q - p)
rate := (a*q^2 - a*p^2)/(q - p);
rate = (a*q^2 - a*p^2)/(q - p);
Δy/Δx = (aq^2 − ap^2)/(q − p)
Shortcut formula for the average rate of change of \(y = ax^{2}\): \(a(p+q)\)
Δy/Δx = a(p + q)
\dfrac{\Delta y}{\Delta x} = a(p + q)
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mrow>
    <mfrac>
      <mrow><mi>&#x394;</mi><mi>y</mi></mrow>
      <mrow><mi>&#x394;</mi><mi>x</mi></mrow>
    </mfrac>
    <mo>=</mo>
    <mi>a</mi>
    <mo>(</mo>
    <mi>p</mi>
    <mo>+</mo>
    <mi>q</mi>
    <mo>)</mo>
  </mrow>
</math>
(Delta y)/(Delta x) = a(p + q)
a (p + q)
rate := a*(p + q);
rate = a*(p + q);
Δy/Δx = a(p + q)

How to have ChatGPT  do the calculation

You are a math calculation assistant for functions. Do the following calculation by actually running Python code, and base your answer only on the numbers from the execution result (do not answer by mental math or guessing).

For the quadratic function y = 2x², find the following two things.
1. The range of y when the domain of x is −1 ≤ x ≤ 3 (also explain why it matters whether the domain includes 0)
2. The average rate of change as x goes from 1 to 3 (show the steps for change in y ÷ change in x, and also use the shortcut formula a(p+q))

In Python, use the fractions module from the standard library to calculate exactly. Show the formulas you used and the numbers from the execution result.

How to Use
  1. 1
    Enter your numbers
    Type the numbers you want to calculate with into the input fields
  2. 2
    Calculate
    Press the "Calculate" button
  3. 3
    Check the result
    The result appears on the spot. The same page also explains the idea behind the calculation and the formula
  DataChef Features
Easy and Free
Unlimited conversions for free.
No technical knowledge required.
Intuitive and user-friendly operation.
No Registration Required
Available immediately after access.
Can be used without registering personal information.
Safe and Secure
Fully SSL encrypted communication.
Automatic file deletion by clicking "download".
Fast
High-speed site access
and rapid file conversion.
No Watermark
No watermark.
No attribution required.
Commercial Use Available
Free for commercial use.
No need to contact us for commercial use permission.