a) \(a^2-b^2-2a+2b\\ =\left(a-b\right)\left(a+b\right)-2\left(a-b\right)\\ =\left(a-b\right)\left(a+b-2\right)\)
b) \(x^2-xy+2y-4\\ =\left(x^2-4\right)+\left(2y-xy\right)\\ =\left(x-2\right)\left(x+2\right)+y\left(2-x\right)\\ =\left(x-2\right)\left(x+2\right)-y\left(x-2\right)\\ =\left(x-2\right)\left(x-y+2\right)\)
Lần sau ghi đề bài chú ý ghi chuẩn nha !
(a-b)(a+b)-2(a-b)
(a-b)(a+b-2)
a) a2 - b2 - 2a + 2b
= (a - b)(a + b) - 2(a - b)
= (a - b)(a + b - 2)
b) x2 - xy + 2y - 4
= (x - y)2 - 22
= (x - y - 2)(x - y + 2)