ПОМОГИТЕ РЕШИТЬ!!!!!!!!

1) $\frac{a+b}{5} - \frac{a}{5}= \frac{a+b-a}{5}= \frac{b}{5}$
2) $\frac{m-n}{a}+ \frac{m+n}{a} = \frac{m-n+m+n}{a} = \frac{2m}{a}$
3) $\frac{ a^{2} }{a+b} - \frac{ b^{2}}{a+b} = \frac{ a^{2} - b^{2} }{a+b}= \frac{(a+b)(a-b)}{a+b}=a-b$
4) $\frac{ c^{2} + d^{2}}{c-d} - \frac{2cd}{c-a} = \frac{ c^{2} + d^{2}-2cd }{c-a} = \frac{ c^{2} -2cd+ d^{2} }{c-a} = \frac{(c-a)^{2} }{c-a}=c-a$
5) $\frac{x}{ x^{2} - y^{2} } - \frac{y}{x^{2} - y^{2}} = \frac{x-y}{ x^{2} - y^{2} } = \frac{x-y}{(x+y)(x-y)}= \frac{1}{x+y}$