Algebra II : Transformations of Polynomial Functions

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #1 : Transformations Of Polynomial Functions

\displaystyle g(x)=4(2x-6)^{5}

What transformations have been enacted upon \displaystyle g(x) when compared to its parent function, \displaystyle f(x)=x^{5}?

Possible Answers:

vertical stretch by a factor of 4

horizontal stretch by a factor of 2

horizontal translation 3 units right

vertical stretch by a factor of 4

horizontal compression by a factor of 2

horizontal translation 6 units right

vertical stretch by a factor of 4

horizontal compression by a factor of 2

horizontal translation 3 units right

vertical stretch by a factor of 4

horizontal stretch by a factor of 2

horizontal translation 6 units right

Correct answer:

vertical stretch by a factor of 4

horizontal compression by a factor of 2

horizontal translation 3 units right

Explanation:

First, we need to get this function into a more standard form.

\displaystyle g(x)=4(2x-6)^{5}

\displaystyle g(x)=4[2(x-3)]^{5}

Now we can see that while the function is being horizontally compressed by a factor of 2, it's being translated 3 units to the right, not 6. (It's also being vertically stretched by a factor of 4, of course.)

Example Question #1 : Transformations Of Polynomial Functions

Define \displaystyle f (x) = 6x -7 and \displaystyle g (x) = 2x + 8 .

Find \displaystyle (g \circ f) (x).

Possible Answers:

\displaystyle (g \circ f) (x) =12 x^{2} -34x -56

\displaystyle (g \circ f) (x) =12 x^{2} -56

\displaystyle (g \circ f) (x) =8x + 1

\displaystyle (g \circ f) (x) = 12x - 6

\displaystyle (g \circ f) (x) = 12x +41

Correct answer:

\displaystyle (g \circ f) (x) = 12x - 6

Explanation:

By definition, \displaystyle (g \circ f) (x) = g (f(x)), so

\displaystyle (g \circ f) (x) = g ( 6x-7 )

\displaystyle = 2 (6x-7) + 8

\displaystyle =12 x-14 + 8

\displaystyle =12 x - 6

Example Question #2 : Transformations Of Polynomial Functions

Define \displaystyle f (x) = 2x + 7 and \displaystyle g(x) = x^{2} - 5.

Find \displaystyle (g \circ f) (x).

Possible Answers:

\displaystyle (g \circ f) (x) = 2 x^{2}-3

\displaystyle (g \circ f) (x) =4 x ^{2} +44

\displaystyle (g \circ f) (x) =4 x ^{2} + 28 x +44

\displaystyle (g \circ f) (x) =4 x ^{2} + 28 x + 54

\displaystyle (g \circ f) (x) = 2 x^{2}-17

Correct answer:

\displaystyle (g \circ f) (x) =4 x ^{2} + 28 x +44

Explanation:

By definition, \displaystyle (g \circ f) (x) = g (f(x)), so

\displaystyle (g \circ f) (x) = g (2x+7)

\displaystyle = \left ( 2x+7\right )^{2} - 5

\displaystyle = \left ( 2x\right )^{2} + 2 \cdot 2x \cdot 7 +7 ^{2} - 5

\displaystyle =4 x ^{2} + 28 x +49 - 5

\displaystyle =4 x ^{2} + 28 x +44

Example Question #1 : Transformations Of Polynomial Functions

Write the transformation of the given function moved five units to the left:

\displaystyle f(x)=x^2+5

Possible Answers:

\displaystyle (x+5)^2+5

\displaystyle (x-5)^2

\displaystyle (x-5)^2+5

\displaystyle x^2

Correct answer:

\displaystyle (x+5)^2+5

Explanation:

To transform the function horizontally, we must make an addition or subtraction to the input, x. Because we are asked to move the function to the left, we must add the number of units we are moving. This is the opposite of what one would expect, but if we are inputting values that are to the left of the original, they are less than what would have originally been. So, to counterbalance this, we add the units of the transformation.

For our function being transformed five units to the left, we get

\displaystyle f(x)=(x+5)^2+5

 

Example Question #602 : Functions And Graphs

Write the transformation of the given function flipped, and moved one unit to the left:

\displaystyle f(x)=x^2+4

Possible Answers:

\displaystyle -[(x-1)^2+4]

\displaystyle -[(x+1)^2+4]

\displaystyle [(x+1)^2+4]

\displaystyle [(x-1)^2+4]

Correct answer:

\displaystyle -[(x+1)^2+4]

Explanation:

To transform a function horizontally, we must add or subtract the units we transform to x directly. To move left, we add units to x, which is opposite what one thinks should happen, but keep in mind that to move left is to be more negative. To flip a function, the entire function changes in sign.

After making both of these changes, we get

\displaystyle -[(x+1)^2+4]

Example Question #1 : Transformations Of Polynomial Functions

Transform the function by moving it two units up, and five units to the left:

\displaystyle f(x)=x^2-1

Possible Answers:

\displaystyle (x-5)^2-1

\displaystyle (x+5)^2-1

\displaystyle (x-5)^2+1

\displaystyle (x+5)^2+1

Correct answer:

\displaystyle (x+5)^2+1

Explanation:

To transform a function we use the following formula,

\displaystyle f(x)=(x-h)^2+v

where h represents the horizontal shift and v represents the vertical shift.

In this particular case we want to shift to the left five units,

\displaystyle h=-5

and vertically up two units,

\displaystyle v=2.

Therefore, the transformed function becomes,

\displaystyle \\f(x)=(x-h)^2+v \\f(x)=(x--5)^2-1+2 \\f(x)=(x+5)^2+1.

Example Question #7 : Transformations Of Polynomial Functions

Shift  \displaystyle y=-2(x+1)^2 up one unit.  What is the new equation?

Possible Answers:

\displaystyle y = -2x^2

\displaystyle y = -2x^2-4x+2

\displaystyle y = -2x^2-4x-2

\displaystyle y = -2x^2-4x-1

\displaystyle y=-2x^2-8x-8

Correct answer:

\displaystyle y = -2x^2-4x-1

Explanation:

Expand the binomial.

\displaystyle (x+1)(x+1) = x^2+2x+1

Multiply negative by this quantity.

\displaystyle -2 (x^2+2x+1) = -2x^2-4x-2

The polynomial in standard form is:  \displaystyle y = -2x^2-4x-2

Shifting this graph up one will change the y-intercept by adding one unit.

The answer is:  \displaystyle y = -2x^2-4x-1

Example Question #4 : Transformations Of Polynomial Functions

Shift the graph \displaystyle y= (6-3x)^2 up two units.  What's the new equation?

Possible Answers:

\displaystyle y=9x^2-36x+38

\displaystyle y=-9x^2+48x+66

\displaystyle y=9x^2+36x+38

\displaystyle y=9x^2-48x+64

\displaystyle y=9x^2-48x+66

Correct answer:

\displaystyle y=9x^2-36x+38

Explanation:

Shifting this parabola up two units requires expanding the binomial.

Use the FOIL method to simplify this equation.

\displaystyle y= (6-3x)^2 = (6-3x)(6-3x)

\displaystyle y=(6)(6)+(6)(-3x)+(-3x)(6)+(-3x)(-3x)

\displaystyle y=36-18x-18x+9x^2

\displaystyle y=9x^2-36x+36

Shifting this graph up two units will add two to the y-intercept.

The answer is:  \displaystyle y=9x^2-36x+38

Example Question #1 : Transformations Of Polynomial Functions

Shift \displaystyle y=(x-4)(x+1) to up two units. What is the new equation?

Possible Answers:

\displaystyle y=x^2-3x-6

\displaystyle x^2-x-12

\displaystyle y=x^2-3x-2

\displaystyle y=x^2-3x+2

\displaystyle y=x^2-3x+6

Correct answer:

\displaystyle y=x^2-3x-2

Explanation:

We will need to determine the equation of the parabola in standard form, which is:

\displaystyle y=ax^2+bx+c

Use the FOIL method to expand the binomials.

\displaystyle (x-4)(x+1) = x^2+x-4x-4 = x^2-3x-4

Shifting this up two units will add two to the value of \displaystyle c.

The answer is:  \displaystyle y=x^2-3x-2

Example Question #1 : Transformations Of Polynomial Functions

If \displaystyle f(x)=2x-5 and \displaystyle g(x)=x^{2}-1, what is \displaystyle g(f(x))?

Possible Answers:

\displaystyle 2x^{2}-5x-24

\displaystyle 4x^{2}-20x+24

\displaystyle 2x^{2}-20x+26

\displaystyle 4x^{2}-10x-24

Correct answer:

\displaystyle 4x^{2}-20x+24

Explanation:

In this problem, the \displaystyle x in the \displaystyle g(x) equation becomes \displaystyle f(x) --> \displaystyle g((2x-5)^{}2-1).

This simplifies to \displaystyle 4x^{}2-20x+25-1, or

\displaystyle 4x^{}2-20x+24

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