phân tích đa thức thành nhân tử a) x²-y²-2x+2y b) 2x+2y-x²-xy c) 3a²-6ab+3b²-12c² d) x²-25+y²+2xy e) a²+2ab+b²-ac-bc

a) $x^2-y^2-2x+2y$

$=(x-y)(x+y)-2(x-y)$

$=(x-y)(x+y-2)$

b) $2x+2y-x^2-xy$

$=2(x+y)-x(x+y)$

$=(x+y)(2-x)$

c) $3a^2-6ab+3b^2-12c^2$

$=3.(a^2-2ab+b^2)-4c^2$

$=3.[(a-b)^2-(2c)^2]$

$=3.(a-b-2c).(a-b+2c)$

d) $x^2-25+y^2+2xy$

$=(x^2+2xy+y^2)-25$

$=(x+y)^2-25$

$=(x+y+5)(x+y-5)$

e) $a^2+2ab+b^2-ac-bc$

$=(a^2+2ab+b^2)-c.(a+b)$

$=(a+b)^2-c.(a+b)$

$=(a+b)(a+b-c)$