a) `3x^4 - x^5 = x^4 (3-x)`
b) `-8x^2y^2 - 12xy^3 - 4xy^2 = -4xy^2 (2x + 3y + 1)`
c) `3x(x-y) - 2y(x-y) = (x-y)(3x-2y)`
d) `a(x+2) - 2b(x+2) + (x+2) = (x+2)(a-2b+1)`
e) `5x(x-y) - (y-x) = 5x(x-y) - [-(x-y)] = 5x(x-y) + (x-y) = (x-y)(5x+1)`
f) `2x(x+3) + 3+x = 2x(x+3) + (x+3) = (x+3)(2x+1)`
g) `7x(x-y) + 2(y-x)^2 = 7x(x-y) + 2(x-y)^2 = (x-y)[7x + 2(x-y)] = (x-y)(9x - 2y)`