Giải thích các bước giải:
$1.\frac{3x-3y}{2x+2y}.\frac{8x+8y}{15x-15}=\frac{3(x-y)}{2(x+y)}.\frac{8(x+y)}{15.(x-1)}=\frac{4x-4y}{5x-5}\\
2.\frac{2x^2-4xy+2y^2}{5x-5y}.\frac{15x^2-15y^2}{4x^3+4y^3}=\frac{2(x-y)^2}{5(x-y)}.\frac{15(x-y)(x+y)}{4(x+y)(x^2-xy+y^2)}=\frac{3(x-y)^2}{2(x^2-xy+y^2)}\\
3.\frac{3-3x}{(1+x)^2}:\frac{6x^2-6}{x+1}=\frac{3(1-x)}{(x+1)^2}.\frac{x+1}{6(x-1)(x+1)}=\frac{-1}{2(x+1)^2}\\
4.\frac{a^4-b^4}{a^3-b^3}:\frac{a^2+b^2}{a^2-b^2}=\frac{(a^2-b^2)(a^2+b^2)}{(a-b)(a^2+ab+b^2)}.\frac{(a+b)(a-b)}{a^2+b^2}=\frac{(a+b)(a^2-b^2)}{a^2+ab+b^2}$
(Hai câu cuối mình giải rồi)
