Glencoe Math: Course 3, Volume 2
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Glencoe Math: Course 3, Volume 2 View details
5. Similar Triangles and Indirect Measurement
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Exercise 23 Page 560

To obtain the image of a vertex after a dilation with scale factor k, multiply its coordinates by k.

Graph:

Coordinates: A'(- 9,3), B'(0,6), C'(6,- 6)

Practice makes perfect

Let's mark the given coordinates and graph the figure.

To find the coordinates of the image after a dilation with a scale factor of k, we multiply each coordinate of the preimage by k.

ccc Preimage & & Image [0.5em] (x,y)& ⇒ & ( kx, ky) Now, let's find the coordinates of the vertices of ABC after a dilation with a scale factor k= 3.

Dilation With Scale Factor k=3
Preimage Multiply by k Image
A(- 3,1) ( 3(- 3), 3(1)) A'(- 9,3)
B(0,2) ( 3(0), 3(2)) B'(0,6)
C(2, - 2) ( 3(2), 3(- 2)) C'(6,- 6)
We can now plot the obtained points and connect them with segments to draw the image.
dilation

Checking Our Answer

To check our answer, we can draw rays from the origin through the vertices of the original figure. The vertices of the dilation should lie on those rays.
drawing rays