Đáp án:+Giải thích các bước giải:
Bài 2:
a) $x^4+4y^4\\=(x^4+4x^2y^2+4y^4)-4x^2y^2\\=(x^2+2y^2)^2-4x^2y^2\\=(x^2+2y^2-2xy)(x^2+2y^2+2xy)$
b) $a^2-b^2-2x(a-b)\\=(a-b)(a+b)-2x(a-b)\\=(a-b)(a+b-2x)$
c) $a^2-b^2-2x(a+b)\\=(a-b)(a+b)-2x(a+b)\\=(a+b)(a-b-2x)$
Bài 3:
a) $x^3+x^2y-xy^2-y^3\\=x^2(x+y)-y^2(x+y)\\=(x+y)(x^2-y^2)\\=(x+y)(x+y)(x-y)\\=(x+y)^2(x-y)$
b) $x^2y^2+1-x^2-y^2\\=(x^2y^2-x^2)-(y^2-1)\\=x^2(y^2-1)-(y^2-1)\\=(y^2-1)(x^2-1)\\=(y-1)(y+1)(x-1)(x+1)$
c) $x^2-y^2-4x+4y\\=(x-y)(x+y)-4(x-y)\\=(x-y)(x+y-4)$
d) $x^2-y^2-2x+2y\\=(x-y)(x+y)-2(x-y)\\=(x-y)(x+y-2)$
e) $x^2-y^2-2x-2y\\=(x-y)(x+y)-2(x+y)\\=(x+y)(x-y-2)$
