Algebra II : Transformations

Study concepts, example questions & explanations for Algebra II

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Example Questions

Example Question #1 : Transformations

\displaystyle f(x)=x^{2}

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

How is the graph of \displaystyle g(x) different from the graph of \displaystyle f(x)?

Possible Answers:

\displaystyle g(x) is narrower than \displaystyle f(x) and is shifted up 3 units

\displaystyle g(x) is wider than \displaystyle f(x) and is shifted down 3 units

\displaystyle g(x) is narrower than \displaystyle f(x) and is shifted to the left 3 units

\displaystyle g(x) is wider than \displaystyle f(x) and is shifted to the right 3 units

\displaystyle g(x) is narrower than \displaystyle f(x) and is shifted down 3 units

Correct answer:

\displaystyle g(x) is narrower than \displaystyle f(x) and is shifted down 3 units

Explanation:

Almost all transformed functions can be written like this:

\displaystyle g(x)=a[f(b(x-c))]+d

where \displaystyle f(x) is the parent function. In this case, our parent function is \displaystyle f(x)=x^{2}, so we can write \displaystyle g(x) this way:

\displaystyle g(x)=a[b(x-c)]^{2}+d

Luckily, for this problem, we only have to worry about \displaystyle a and \displaystyle d.

\displaystyle a represents the vertical stretch factor of the graph.

  • If \displaystyle |a| is less than 1, the graph has been vertically compressed by a factor of \displaystyle |a|. It's almost as if someone squished the graph while their hands were on the top and bottom. This would make a parabola, for example, look wider.
  • If \displaystyle |a| is greater than 1, the graph has been vertically stretched by a factor of \displaystyle |a|. It's almost as if someone pulled on the graph while their hands were grasping the top and bottom. This would make a parabola, for example, look narrower.

\displaystyle d represents the vertical translation of the graph.

  • If \displaystyle d is positive, the graph has been shifted up \displaystyle d units.
  • If \displaystyle d is negative, the graph has been shifted down \displaystyle d units.

 

For this problem, \displaystyle a is 4 and \displaystyle d is -3, causing vertical stretch by a factor of 4 and a vertical translation down 3 units.

Example Question #2 : Transformations

Which of the following transformations represents a parabola shifted to the right by 4 and halved in width?

Possible Answers:

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

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

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

\displaystyle f(x) = 0.5(x-4)^2

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

Correct answer:

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

Explanation:

Begin with the standard equation for a parabola: \displaystyle f(x)=x^2.

Horizontal shifts are represented by additions (leftward shifts) or subtractions (rightward shifts) within the parenthesis of the \displaystyle x term. To shift 4 units to the right, subtract 4 within the parenthesis.

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

The width of the parabola is determined by the magnitude of the coefficient in front of \displaystyle x. To make a parabola narrower, use a whole number coefficient. Halving the width indicates a coefficient of two.

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

Example Question #1 : Transformations

Which of the following represents a standard parabola shifted up by 2 units?

Possible Answers:

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

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

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

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

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

Correct answer:

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

Explanation:

Begin with the standard equation for a parabola: \displaystyle f(x)=x^2.

Vertical shifts to this standard equation are represented by additions (upward shifts) or subtractions (downward shifts) added to the end of the equation. To shift upward 2 units, add 2.

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

Example Question #4 : Transformations

Which of the following transformation flips a parabola vertically, doubles its width, and shifts it up by 3?

Possible Answers:

\displaystyle f(x)=-2x^2 +3

\displaystyle f(x)=-(0.5x^2 +3)

\displaystyle f(x)=-0.5x^2 +1.5

\displaystyle f(x)=-0.5x^2 +3

\displaystyle f(x)=-2(x^2 +3)

Correct answer:

\displaystyle f(x)=-0.5x^2 +3

Explanation:

Begin with the standard equation for a parabola: \displaystyle f(x)=x^2.

Inverting, or flipping, a parabola refers to the sign in front of the coefficient of the \displaystyle x. If the coefficient is negative, then the parabola opens downward.

\displaystyle f(x)=-x^2

The width of the parabola is determined by the magnitude of the coefficient in front of \displaystyle x. To make a parabola wider, use a fractional coefficient. Doubling the width indicates a coefficient of one-half.

\displaystyle f(x)=-(\frac{1}{2})x^2=-0.5x^2

Vertical shifts are represented by additions (upward shifts) or subtractions (downward shifts) added to the end of the equation. To shift upward 3 units, add 3.

\displaystyle f(x)=-0.5x^2 +3

Example Question #2 : Transformations

Which of the following shifts a parabola six units to the right and five downward?

Possible Answers:

\displaystyle f(x)=(x-6)^2-5

\displaystyle f(x)=(x-\sqrt{6})^2-5

\displaystyle f(x)=(x+6)^2-5

\displaystyle f(x)=(x-\sqrt{5})^2+6

\displaystyle f(x)=(x-5)^2-6

Correct answer:

\displaystyle f(x)=(x-6)^2-5

Explanation:

Begin with the standard equation for a parabola: \displaystyle f(x)=x^2.

Vertical shifts to this standard equation are represented by additions (upward shifts) or subtractions (downward shifts) added to the end of the equation. To shift downward 5 units, subtract 5.

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

Horizontal shifts are represented by additions (leftward shifts) or subtractions (rightward shifts) within the parenthesis of the \displaystyle x term. To shift 6 units to the right, subtract 6 within the parenthesis.

\displaystyle f(x)=(x-6)^2 - 5

Example Question #3 : Transformations

Which of the following transformations represents a parabola that has been flipped vertically, shifted to the right 12, and shifted downward 4?

Possible Answers:

\displaystyle f(x)=-(x+12)^2-4

\displaystyle f(x)=-[(x+12)^2-4]

\displaystyle f(x)=-[(x+12)^2+4]

\displaystyle f(x)=-(x-12)^2-4

\displaystyle f(x)=-(x+12)^2+4

Correct answer:

\displaystyle f(x)=-(x-12)^2-4

Explanation:

Begin with the standard equation for a parabola: \displaystyle f(x)=x^2.

Horizontal shifts are represented by additions (leftward shifts) or subtractions (rightward shifts) within the parenthesis of the \displaystyle x term. To shift 12 units to the right, subtract 12 within the parenthesis.

\displaystyle f(x) = (x-12)^2

Inverting, or flipping, a parabola refers to the sign in front of the coefficient of the \displaystyle x. If the coefficient is negative, then the parabola opens downward.

\displaystyle f(x) = -(x-12)^2

Vertical shifts are represented by additions (upward shifts) or subtractions (downward shifts) added to the end of the equation. To shift downward 4 units, subtract 4.

\displaystyle f(x) = -(x-12)^2 - 4

Example Question #4 : Transformations

Which of the following transformations represents a parabola that has been shifted 4 units to the left, 5 units down, and quadrupled in width?

Possible Answers:

\displaystyle f(x) = 0.25(x-4)^2+5

\displaystyle f(x) = 0.25(x+4)^2-5

\displaystyle f(x) = 0.25(x-4)^2-5

\displaystyle f(x) = 4(x-4)^2-5

\displaystyle f(x) = 4(x+4)^2-5

Correct answer:

\displaystyle f(x) = 0.25(x+4)^2-5

Explanation:

Begin with the standard equation for a parabola: \displaystyle f(x)=x^2.

Horizontal shifts are represented by additions (leftward shifts) or subtractions (rightward shifts) within the parenthesis of the \displaystyle x term. To shift 4 units to the left, add 4 within the parenthesis.

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

The width of the parabola is determined by the magnitude of the coefficient in front of \displaystyle x. To make a parabola wider, use a fractional coefficient. Doubling the width indicates a coefficient of one-fourth.\displaystyle f(x) = \frac{1}{4}(x+4)^2=0.25(x+4)^2

Vertical shifts are represented by additions (upward shifts) or subtractions (downward shifts) added to the end of the equation. To shift downward 5 units, subtract 5.

\displaystyle f(x) = 0.25(x+4)^2 - 5

Example Question #1 : Transformations

If the function \displaystyle y=1-x is shifted left 2 units, and up 3 units, what is the new equation?

Possible Answers:

\displaystyle y=x-2

\displaystyle y=-1-x

\displaystyle y=3-x

\displaystyle y=4-x

\displaystyle y=2-x

Correct answer:

\displaystyle y=2-x

Explanation:

Shifting \displaystyle y=1-x left 2 units will change the y-intercept from \displaystyle (0,1) to \displaystyle (0.-1).

The new equation after shifting left 2 units is:

\displaystyle y=1-(x+2)=-1-x

Shifting up 3 units will add 3 to the y-intercept of the new equation.

The answer is:  \displaystyle y=2-x

 

Example Question #1 : Transformations

If \displaystyle f(x)=x^2, what is \displaystyle -f(x)?

Possible Answers:

It is the same as \displaystyle f(x).

It is the \displaystyle x^2 parabola reflected across the x-axis.

It is the \displaystyle x^2 parabola shifted to the right by 1.

It is the \displaystyle x^{-2} function.

It is the \displaystyle x^2 parabola reflected across the y-axis.

Correct answer:

It is the \displaystyle x^2 parabola reflected across the x-axis.

Explanation:

It helps to evaluate the expression algebraically.

\displaystyle -f(x)=-x^2. Any time you multiply a function by a -1, you reflect it over the x axis. It helps to graph for verification.

This is the graph of \displaystyle x^2

X 2

and this is the graph of \displaystyle -x^2

 x 2

Example Question #2 : Transformations

If \displaystyle f(x)=e^x, what is \displaystyle f(-x)?

Possible Answers:

It is the \displaystyle e^x graph shifted 1 to the right.

It is the \displaystyle e^x graph reflected across the y-axis.

It is the \displaystyle -e^x graph.

It is the \displaystyle e^x graph reflected across the x-axis.

It is the \displaystyle e^x graph rotated about the origin.

Correct answer:

It is the \displaystyle e^x graph reflected across the y-axis.

Explanation:

Algebraically, \displaystyle f(-x)=e^{-x}.

This is a reflection across the y axis.

This is the graph of \displaystyle e^x

E x

And this is the graph of \displaystyle e^{-x}

 

E  x

 

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