Помогите пожалуйста № 880

[latex] \frac{a-b}{a^3-b^3} = \frac{a-b}{(a-b)(a^2+ab+b^2)} = \frac{1}{a^2+ab+b^2} \\ \\ \frac{p^3+q^3}{2p+2q} = \frac{(p+q) (p^2-pq+q^2)}{2(p+q)} = \frac{p^2-pq+q^2}{2} \\ \\ \frac{x^3-y^3}{x^2-y^2} = \frac{x^2+xy+y^2}{x+y} \\ \\ \frac{a^2+2ab+b^2}{a^3+b^3} = \frac{(a+b)^2}{(a+b)(a^2-ab+b^2)} = \frac{a+b}{a^2-ab+b^2} \\ \\ \frac{m^2+n^3}{2(m^2-mn+n^2)} = \frac{m+n}{2} \\ \\ \frac{a^2-az}{a^3-z^3} = \frac{a(a-z)}{(a-z)(a^2+az+z^2)} = \frac{a}{a^2+az+z^2} [/latex]