7x - (25x^2 + 12x) = 7x - 25x^2 - 12x = -25x^2 - 5x
Given:
The point is B(2,5) and its image is B'(1,2.5).
To find:
The scale factor.
Solution:
If a figure is dilated by the scale factor k and (0,0) is the center of then the scale factor is defined as

x-coordinate of point B' is 1 and the x-coordinate of point B is 2. So, the scale factor is

Therefore, the scale factor is
and the correct option is D.
The answers are
1. B
2. B
3. C