Question

What are the coordinates of R' after a dilation by a scale factor of 3, centered at the origin, followed by the translation (x, y) - (x, y + 3)?
A. (9, 8)
B. (12, 18)
C. (9, 18)
D. (9, 24)​

Answer 1

9514 1404 393

Answer:

  C.  (9, 18)

Step-by-step explanation:

Given R(3, 5), a dilation by a factor of 3 will multiply each coordinate to give ...

  (9, 15)

Then the translation up by 3 will give you the image coordinates ...

  (x, y) ⇒ (x, y+3)

  (9, 15) ⇒ (9, 15 +3) = (9, 18)

The coordinates of R' are (9, 18), matching choice C.

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Comment on multiple choice answers

As it often does, here it works to "guess" the answer that has the coordinates that are most-repeated. An x-coordinate of 9 is part of 3 answer choices; a y-coordinate of 18 is the only repeated value in the answer choices. If you were to guess, an appropriate guess would be (9, 18). That happens to be correct in this case.