Unit 3 Transformations Review

Match the following vocabulary words with their definition.

• The symbol used to identify which figure is the NEW one.

• Preimage

• The figure you END with on the transformation.

• Image

• The figure you START with on the transformation.

• Prime

Is the BLUE figure the Image or Preimage?

• Image

• Preimage

• I can't tell!

Answer explanation

The preimage is the original, like "pre" is before. Its points will have regular letters like A, B, C.

The image is the change. Its points will have primes on the letters like A', B' and C'.

Which vector describes the translation pictured?

(x, y) --> (x + a, y + b)

• < -4, 9 >

• < 4, -9 >

• < 9, -4 >

• < -9, 4 >

Answer explanation

Vector Rule:

<change to x, change to y>

From A to A', we move right first, then down.

Point X (-1, 4) is translated by the vector < -3, -9 >

What is the coordinate of Point X'?

• (-5, -4)

• (-1, -7)

• (-4, -5)

• (-1, 5)

Answer explanation

The vector < -3, -9 > tells us to move left 3 and down 9.

OR to subtract 3 from the x, and subtract 9 from the y coordinate.

K = (1, -4)

Find K' if the figure is reflected across the x-axis.

(x, y) --> (x, -y)

• (4, 1))
• (-1, -4)
• (1, -4)
• (1, 4)

Answer explanation

The rule (x, y) --> (x, -y) means to keep the x-coordinate, but change the sign on the y-coordinate.

Point A = (1, 2)

Where will A' be if triangle ABC is reflected across the y-axis?

(x, y) --> (-x, y)

• (2, 1)

• (1, -2)

• (-1, 2)

Answer explanation

The rule (x, y) --> (-x, y) means to change the sign on the the x-coordinate, but keep the y-coordinate as is.

What type of rotation does this represent (from red to blue)?

• 270⁰ clockwise around the origin

• 90⁰ counter clockwise around the origin

• 180⁰ clockwise around the origin

If your scale factor, k = 2.5, what type of dilation is it?

• Reduction

• Enlargement

Answer explanation

Scale factors greater than 1 will enlarge the image.

If your scale factor, k = 0.8, what type of dilation is it?

• Reduction

• Enlargement

Answer explanation

Scale factors less than 1 will reduce the image.

What is the formula for scale factor?