We are going to evaluate a vertex of both forms.
blue shape:
(-5.10)
black shape:
(-1,2)
As one figure is the dilatation of another then:
k (-1,2) = (- 5,10)
From here we know:
-k = -5
Equivalently:
2k = 10
Where we conclude:
k = 5
Answer:
The scale factor of the dilation is:
k = 5
