Answer:
dilation by a factor of 3 about (1, 0)
Explanation:
You have correctly surmised that Q is a dilation of P by a factor of 3. The center of dilation is not the origin, so the trick is to figure out where it is.
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An original point and its dilated image are always on the same line through the center of dilation. Here, that center can be found by drawing lines through the corresponding vertices. The attachment shows the center of dilation is (1, 0) on the x-axis.
The single transformation is ...
dilation by a factor of 3 about the point (1, 0).
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Additional comment
You can check this by seeing that each image point is 3 times as far from this center as the corresponding original point.