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Algebra 2 · Mathematics
Functions · Real functions

Transformations of Functions

Before you start, make sure you know: Basic concepts (Algebra 1)
Before you start, make sure you know: Representation of functions (Algebra 1)

Emma and Jayden hike the same trail at the same steady pace, but Jayden leaves 10 minutes after Emma. Their distance graphs have exactly the same shape. One is just slid over. Recognizing "same picture, moved or reshaped" saves you from studying a function from scratch every time. By the end of this page you will be able to write Jayden's distance in terms of Emma's.

Shifts: sliding a graph without changing its shape

A parabola y = f(x) with vertex at the origin and a copy shifted 3 units right and 2 units up, with the vertex path marked. right 3 up 2 y = f(x) y = f(x − 3) + 2

Try the sliders and watch where the vertex goes.

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Given the function $f(x) = x^2 - 3x$, write the algebraic expression of the function $g(x)$ obtained by translating the graph of $f(x)$ four units to the left and two…

Given the function $f(x) = x^2 - 3x$, write the algebraic expression of the function $g(x)$ obtained by translating the graph of $f(x)$ four units to the left and two units upward.

Solve
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A hot air balloon descends at a constant speed. Its altitude in feet is given by $A(t) = 800 - 50t$, where $t$ is the time in minutes. A second balloon begins its…

A hot air balloon descends at a constant speed. Its altitude in feet is given by $A(t) = 800 - 50t$, where $t$ is the time in minutes. A second balloon begins its descent $10$ minutes later with exactly the same flight profile. Write the expression for the altitude of the second balloon $B(t)$ as a function of $A(t)$ and expand its final algebraic expression.

Solve

Stretches, compressions, and reflections

New function What happens to the point $(x, y)$ on $f$
$f(x) + k$ $(x, y + k)$
$f(x - h)$ $(x + h, y)$
$a\,f(x)$ $(x, ay)$
$f(bx)$ $\left(\dfrac{x}{b}, y\right)$
$-f(x)$ $(x, -y)$
$f(-x)$ $(-x, y)$

Move the slider $a$ to see vertical scaling. Negative values reflect.

Now compare with horizontal scaling. Notice that the $y$-intercept does not move, but the $x$-intercepts do.

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The graph of a function $f(x)$ passes through the point $P(-3, 5)$. Determine the coordinates of the corresponding point on the graphs of the following transformed…

The graph of a function $f(x)$ passes through the point $P(-3, 5)$. Determine the coordinates of the corresponding point on the graphs of the following transformed functions:

  • $g(x) = -f(x)$

  • $h(x) = f(-x)$

  • $i(x) = 2f(x)$

  • $j(x) = f(x) - 4$

Solve
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Given the elementary function $f(x) = \frac{1}{x}$, state which geometric transformations (translations, stretches, reflections) must be applied successively, and in…

Given the elementary function $f(x) = \frac{1}{x}$, state which geometric transformations (translations, stretches, reflections) must be applied successively, and in what order, to obtain the function $g(x) = -\frac{3}{x} + 2$.

Solve
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The function $C(x)$ represents the cost in dollars of producing $x$ electronic components. Due to a technological improvement in the assembly line, it is now possible to…

The function $C(x)$ represents the cost in dollars of producing $x$ electronic components. Due to a technological improvement in the assembly line, it is now possible to produce triple the number of components for exactly the same total cost. Express the new cost function $N(x)$ in terms of the original function $C(x)$.

Solve

Combining transformations: order matters

Four boxes in a row showing the order of transformations: horizontal scale, horizontal shift, vertical scale, vertical shift. 1. Horizontalscale: f(bx) 2. Horizontalshift: x − h 3. Verticalscale: a · f 4. Verticalshift: + k inside the parentheses first, outside after

If you shift first and scale second, the shift is measured in the original units and then gets scaled. For $f(x) = x^2$ and $g(x) = (2x - 10)^2$, one route is: compress by $\tfrac12$ (giving $(2x)^2$), then shift right 5: $\big(2(x-5)\big)^2$. The other route is: shift right 10 first (giving $(x - 10)^2$), then compress by $\tfrac12$ (replace $x$ with $2x$): $(2x - 10)^2$. Same graph, but the shift is 5 in one order and 10 in the other. Factoring first keeps this straight.

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Given the elementary function $f(x) = \sqrt{x}$, we want to obtain the function $g(x) = \sqrt{4x - 12} + 5$. Explain in detail two different sequences of geometric…

Given the elementary function $f(x) = \sqrt{x}$, we want to obtain the function $g(x) = \sqrt{4x - 12} + 5$.

Explain in detail two different sequences of geometric transformations (altering the order of the horizontal translations and stretches) that allow $g(x)$ to be obtained from $f(x)$. Prove algebraically that both sequences lead to the same expression.

Solve
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A parabola has its vertex at the origin and passes through the point $(2, 4)$. The following transformations are applied to it sequentially: 1. A horizontal compression…

A parabola has its vertex at the origin and passes through the point $(2, 4)$. The following transformations are applied to it sequentially:

  1. A horizontal compression that multiplies the x-coordinates of its points by $\frac{1}{3}$.

  2. A translation of $5$ units to the left.

  3. A reflection across the x-axis.

  4. A translation of $7$ units upward.

Find the analytical expression of the final function $g(x)$ and determine the exact coordinates of its new vertex and its points of intersection with the axes.

Solve
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An engineer designs the profile of a suspension bridge using the curve $f(x) = e^{-x^2}$ as a model. Due to the geological requirements of the terrain, they need to…

An engineer designs the profile of a suspension bridge using the curve $f(x) = e^{-x^2}$ as a model. Due to the geological requirements of the terrain, they need to propose a new profile $g(x) = a \cdot f(b \cdot x - c) + d$ that simultaneously meets the following conditions:

  • It must be twice as wide as the original design.

  • The center of symmetry of the bridge must be translated $4$ units to the right.

  • The profile must be inverted (opening upward instead of downward), without changing its vertical scale.

  • The minimum height of the new profile must be situated exactly $10$ feet above ground level.

Determine analytically the precise values of the parameters $a$, $b$, $c$ and $d$.

Solve

Where do points, domain, and range go?

To find the domain of $g$, find the $x$-values that put the inside of $f$ in the domain of $f$. To find the range, apply the vertical changes ($a$ and $k$) to the range of $f$. If $a < 0$ the endpoints swap order.

The picture shows the bounding boxes for a function $f$ and for $g(x) = f(x - 2) + 1$.

Two rectangles: the domain and range box of f, and the same box shifted 2 units right and 1 unit up for g(x) = f(x − 2) + 1. g: domain [−2, 6], range [−1, 4] f: domain [−4, 4], range [−2, 3]
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Observe the graph of the function $f(x)$ defined in the interval $[-4, 4]$. Determine the domain and the range of the transformed function $g(x) = f(x-3) + 1$.

Observe the graph of the function $f(x)$ defined in the interval $[-4, 4]$. Determine the domain and the range of the transformed function $g(x) = f(x-3) + 1$.

X Y −4 (−2, 3) (1, −2) 4 f(x)
Solve
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The graph of the function $f(x)$ is formed by two line segments joining the points $(-4, -2)$, $(0, 4)$ and $(4, -2)$. A new function is defined by the transformation…

The graph of the function $f(x)$ is formed by two line segments joining the points $(-4, -2)$, $(0, 4)$ and $(4, -2)$. A new function is defined by the transformation $g(x) = -f\left(\frac{x}{2}\right) + 3$.

  • Describe the ordered sequence of geometric transformations applied to $f(x)$.

  • Calculate the exact coordinates of the new vertices of the graph of $g(x)$.

X Y (−4, −2) (0, 4) (4, −2) f(x)
Solve
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Given an arbitrary function $f(x)$ whose domain is the interval $[-6, 8]$ and whose range is the interval $[-4, 12]$, a new function is defined by the expression…

Given an arbitrary function $f(x)$ whose domain is the interval $[-6, 8]$ and whose range is the interval $[-4, 12]$, a new function is defined by the expression $h(x) = -2f\left(3 - \frac{x}{2}\right) + 5$.

Calculate, showing your reasoning and detailing the effects of each applied transformation, the domain and the range of the function $h(x)$.

Solve

Absolute value transformations

The parabola y = x² − 4 drawn dashed, and its absolute value drawn solid, where the part below the x-axis is reflected upward. (0, −4) (0, 4) y = f(x) y = |f(x)|

Where $f$ crosses the $x$-axis, $|f|$ usually gets a corner. Points on the axis stay put, and a point $(x, y)$ with $y < 0$ moves to $(x, -y)$.

For the line $f(x) = x - 1$, these versions look quite different:

Function Shape Key points
$\lvert x - 1\rvert$ V vertex $(1, 0)$
$\lvert x\rvert - 1$ V vertex $(0, -1)$, $x$-intercepts $\pm 1$
$\big\lvert\,\lvert x\rvert - 1\big\rvert$ W zeros at $\pm 1$, local max at $(0, 1)$
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From the graph of the function $f(x)$ shown in the figure, describe the geometric steps necessary to obtain the graph of the function $g(x) = |f(x)|$ and calculate the…

From the graph of the function $f(x)$ shown in the figure, describe the geometric steps necessary to obtain the graph of the function $g(x) = |f(x)|$ and calculate the coordinates of the new vertices or points of inflection.

X Y 2 −4 f(x)
Solve
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Express the function $g(x) = |-x^2 + 4|$ as a piecewise-defined function, removing the modulus and clearly indicating the intervals where the original expression changes…

Express the function $g(x) = |-x^2 + 4|$ as a piecewise-defined function, removing the modulus and clearly indicating the intervals where the original expression changes sign.

Solve
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Match each of the analytical expressions with the corresponding panel in the figure, knowing that they all derive from modulus transformations applied to the base…

Match each of the analytical expressions with the corresponding panel in the figure, knowing that they all derive from modulus transformations applied to the base function $y = x - 3$.

  1. $y = |x| - 3$

  2. $y = ||x-3| - 2|$

  3. $y = ||x| - 3|$

  4. $y = |x-3| - 2$

A B C D
Solve

Transformations in real models

In a model, the input is usually time or quantity and the output is a cost, altitude, or profit. This tells you which kind of change to use.

Slide $d$ to delay the second function.

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The monthly profit of a small tech company, in thousands of dollars, is modeled by the function $B(x) = -2x^2 + 12x - 10$, where $x$ represents the month of the year…

The monthly profit of a small tech company, in thousands of dollars, is modeled by the function $B(x) = -2x^2 + 12x - 10$, where $x$ represents the month of the year ($x=1$ for January, etc.). The company decides to delay the launch of its marketing campaign by one month, which means a horizontal translation of the profit curve, and also assumes an increase in fixed costs of $3$ thousand dollars per month. Find the new expression for the profit function $N(x)$ and determine in which month the maximum profit will now be reached.

Solve
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The efficiency of a solar panel throughout the day is given by a function $E(t)$. A new model of panel is installed that starts generating energy $2$ hours earlier and,…

The efficiency of a solar panel throughout the day is given by a function $E(t)$. A new model of panel is installed that starts generating energy $2$ hours earlier and, due to a special graphene coating, generates $15\%$ more energy at each equivalent instant. Express the new efficiency function $N(t)$ in terms of $E(t)$. If the original panel reached its maximum efficiency at 2:00 p.m., at what time will the new panel reach it?

Solve
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A culture of bacteria grows according to the function $N(t) = 200 \cdot 3^{t/2}$, where $t$ is the time in hours. A second culture $M(t)$ starts with a quarter of the…

A culture of bacteria grows according to the function $N(t) = 200 \cdot 3^{t/2}$, where $t$ is the time in hours. A second culture $M(t)$ starts with a quarter of the initial population of the first, but its growth rate is identical and it started being measured $4$ hours earlier. Express $M(t)$ in terms of $N(t)$ and simplify the resulting expression to check if both populations will be equal at any point.

Solve

Sine waves and periodic transformations

Absolute value changes the period. The solid curve below is $|\sin x|$, whose negative humps are flipped up.

The graph of y = sin x drawn dashed and y = absolute value of sin x drawn solid over 0 to 2π, showing that the absolute value repeats every π. y = |sin x| period π π 2π y = sin x

For $y = |a \sin(bx)|$ the period is $\dfrac{\pi}{|b|}$ (half as long), the range is $[0, |a|]$, and the maxima occur at the same $x$-values where $a\sin(bx)$ reaches $\pm |a|$. For example, $y = |3\sin(2x)|$ has period $\tfrac{\pi}{2}$ and maxima of 3 at $x = \tfrac{\pi}{4} + n\cdot\tfrac{\pi}{2}$.

If a quantity oscillates around a mean value $k$, then $|L(t) - k|$ measures how far it is from the mean. Subtracting $k$ puts the midline on the $x$-axis, and the absolute value folds it.

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In an acoustics study, a base sound wave is modelled by the function $S(t) = \sin(t)$. For an experiment, the original wave is amplified by multiplying its amplitude by…

In an acoustics study, a base sound wave is modelled by the function $S(t) = \sin(t)$. For an experiment, the original wave is amplified by multiplying its amplitude by $4$ and is made higher-pitched by doubling its frequency. In addition, a delay of $\frac{\pi}{4}$ seconds is introduced in the emission. Write the analytical expression of the new sound wave $W(t)$ and calculate its new period.

Solve
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The figure shows the light curve of a variable star, modelled by the function $L(t) = 4 \sin\left(\frac{\pi}{6}t\right) + 10$, where $t$ is measured in days and $L$ in…

The figure shows the light curve of a variable star, modelled by the function $L(t) = 4 \sin\left(\frac{\pi}{6}t\right) + 10$, where $t$ is measured in days and $L$ in units of luminosity. A dense cloud of cosmic dust obscures the star in such a way that the observed luminosity $O(t)$ from Earth is exactly the modulus of the difference between $L(t)$ and its mean luminosity.

Determine the analytical expression of $O(t)$, calculate its new period and find at what instants $t \in [0, 12]$ the observed luminosity is maximum.

t (days) L(t) 10 14 3 6 9 12 L(t)
Solve

Rational functions and symmetry about a point

Many rational functions are secretly transformations of $y = \dfrac{1}{x}$. Divide to reveal them.

For the example above, $f(x + 2) - 3 = \dfrac{3(x+2) - 1}{x} - 3 = \dfrac{3x + 5}{x} - 3 = \dfrac{5}{x}$, which is odd. So the graph is symmetric about $(2, 3)$, the intersection of its two asymptotes.

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Express the rational function $f(x) = \frac{2x + 7}{x + 1}$ in the form $f(x) = k + \frac{m}{x+1}$, by carrying out polynomial division. From this result, describe step…

Express the rational function $f(x) = \frac{2x + 7}{x + 1}$ in the form $f(x) = k + \frac{m}{x+1}$, by carrying out polynomial division. From this result, describe step by step the geometric transformations that must be applied to the rectangular hyperbola $y = \frac{1}{x}$ to obtain the graph of $f(x)$.

Solve
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Find the values of the parameters $a$ and $b$ so that the graph of the rational function $f(x) = \frac{ax + 3}{x + b}$ is symmetric about the point $C(4, 2)$. Hint:…

Find the values of the parameters $a$ and $b$ so that the graph of the rational function $f(x) = \frac{ax + 3}{x + b}$ is symmetric about the point $C(4, 2)$.

Hint: Remember that a function $f(x)$ is symmetric about a point $(h, k)$ if the function translated to the origin, $g(x) = f(x+h) - k$, turns out to be an odd function.

Solve

Even, odd, and periodic functions after a transformation

Recall: $f$ is even if $f(-x) = f(x)$ (symmetric about the $y$-axis), odd if $f(-x) = -f(x)$ (symmetric about the origin), and periodic with period $T$ if $f(x + T) = f(x)$ for all $x$.

To test a new function $g$, compute $g(-x)$ by replacing every $x$ with $-x$, then use what you know about $f$ to rewrite it. Compare with $g(x)$ and $-g(x)$.

An even function that is shifted sideways is usually no longer even, as the parabolas above show. But combinations of shifted copies can still be symmetric.

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Let $f(x)$ be an odd, periodic real function with period $T=6$. From it, the transformed function $g(x) = f(x-2) + f(x+2)$ is defined. Prove analytically whether the…

Let $f(x)$ be an odd, periodic real function with period $T=6$. From it, the transformed function $g(x) = f(x-2) + f(x+2)$ is defined.

Prove analytically whether the function $g(x)$ is even, odd or neither. Also determine whether $g(x)$ is periodic and, if so, calculate its minimum period.

Solve

New coordinate systems and ellipses

Instead of moving a graph, you can move the axes. Moving the origin to the right is equivalent to moving the graph to the left. To change coordinates, write the old coordinates $(x, y)$ in terms of the new ones $(X, Y)$, then substitute into the equation.

A related situation: all conic-style curves can be built by transformations of one simple curve. The semicircle $y = \sqrt{1 - x^2}$ becomes the upper half of an ellipse with horizontal semi-axis $a$ and vertical semi-axis $b$ by stretching horizontally by $a$ (replace $x$ with $x/a$) and vertically by $b$.

Adjust the semi-axes and center to see the ellipse change.

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Let the function be $f(x) = \ln(x)$. A change of reference system is made in the Cartesian plane so that the new origin is located at the point $(-3, 2)$ of the old…

Let the function be $f(x) = \ln(x)$. A change of reference system is made in the Cartesian plane so that the new origin is located at the point $(-3, 2)$ of the old system, the positive direction of the x-axis is reversed, and the unit of measurement of the y-axis is halved. Write the equation of the curve in the new coordinate system.

Solve
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A programmed trajectory for a robotic arm is given by the function $y = \sqrt{R^2 - x^2}$, which describes a semicircle of radius $R$ centred at the origin. The design…

A programmed trajectory for a robotic arm is given by the function $y = \sqrt{R^2 - x^2}$, which describes a semicircle of radius $R$ centred at the origin. The design team wishes to program a new elliptical trajectory $E(x)$ that has its center at the point $(h, k)$, a horizontal semi-axis of length $a$ and a vertical semi-axis of length $b$ (representing only the upper half of the ellipse).

Express the final function $E(x)$, clearly indicating the composition of geometric transformations applied to the base function $y = \sqrt{1 - x^2}$ (semicircle of radius $1$).

Solve

Back to the start: If $E(t)$ is Emma's distance on the trail after $t$ minutes, Jayden leaves 10 minutes later, so his distance is $J(t) = E(t - 10)$: the same graph shifted 10 units to the right.

Summary

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