Answer:
The dilation scale factor is
.
Step-by-step explanation:
The image is the dilated form of its preimage if and only if the following conditions are observed:
1) 
2) 
3) 
4) 
5) 
If we know that
,
,
,
,
,
,
and
, then the coefficients are, respectively:
,
,
, 
As
, we conclude that the dilation scale factor applied in the preimage is equal to
.