How do I do this...?

Question

I'm in 9th grade, in honors geometry. My teacher tried to explain how to find the scale factor with the center's coordinates and the original point's coordinates, but I don't understand! He said that you need to find the prime of the original point, but how would that possibly help me find the scale factor?

Answer 1

I think by "prime" he meant the new point that the original point was transformed to after the scaling was done.

 

So first, find the distance from the original point to the center.

 

Then find the distance from the new point (the "prime of the original point") to the center.

 

(BUT...  Did the center move when the scaling was done?  If so then the second distance has to be from the new point to the new center!)

 

The scaling factor is the new distance divided by the original distance.