4.
(2x - 5) - (3 - 6x) + (4x + 1) = 2x - 5 - 3 + 6x + 4x + 1 = 12 x - 7
5.
(-2x - 4y)(5x + 9y) = -10x^2 - 18xy - 20xy - 36y^2 = -10x^2 -38xy - 36y^2
6.
14xy^2 + 2xy - 6x = 2x(7y^2 + y - 3)
7.
10(x^2/2 - y^2/5)
8.
a) (x + 5)^2 = x^2 + 10x + 25
b) (2x + 3)^2 = 4x^2 + 12x + 9