\(\displaystyle 6xy^2 \, - \, 42y^2 \, - 4x \, + \, 28\)
Bring out (x-7) in the first half:
\(\displaystyle 6xy^2 \, - \, 42y \, = \, 6y^2(x - 7)\)
Bring out (x-7) in the second half:
- 4x + 28 = -4(x - 7)
So we have
\(\displaystyle 6y^2(x - 7) \, - \, 4(x - 7)\)
Easier example:
6b(a) - 4(a) = (6b - 4)a, right?
Can you proceed?
(Yes, Denis, we'll bring out the 2!!!)