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Need help with dilations mix

1 Answer

5 votes

When you add/subtract values to the coordinates of a figure, its size doesn't change, you only move it to another location.

When you multiply the coordinates of a figure, you enlarge it, i.e. create a bigger figure proportional to the original one.

When you divide the coordinates of a figure, you reduce its size.

Since the figure was dilated and not moved, option F is incorrect.

To determine how much it was dilated select any point from the pre image and image and compare them.

For example

G (-2,1)

G'(-5,2.5)

To determine the coefficient used for the dilation divide the x-coordinate of the image point by the x-coordinate of the preimage point:


(X_(G^(\prime)))/(X_G)=(-5)/(-2)=(5)/(2)

Now do the same to determine the coefficient used in the Y-coordinates:


(Y_(G^(\prime)))/(Y_G)=(2.5)/(1)=2.5

2.5 expressed in fractions is 5/2

So the dilation made was (X,Y)→(2/5X,2/5Y)

The correct answer is E.

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