Explanatory variable, or the independent variable. The two are interchangeable, but explanatory is more likely to be used in statistics, and independent variable is used practically everywhere else.
Answer:
a) ΔF'G'H' is the image of ΔFGH
b)Center of dilation (7,-1)
c) Scale factor: 
Step-by-step explanation:
Question a
Since the smaller triangle is named F'G'H', it means that, it is the image of triangle FGH.
Question B.
To find the center of dilation, draw straight lines through any two corresponding points.
The straight lines will meet at (7,-1).
This is called the center of dilation.
See graph in attachment.
Question c
The scale factor of the dilation is given by;





