Решите плииииз, срочно надо

$1) \frac{3 x^{2} -xy}{x-y}- \frac{2 x^{2} +y ^{2} }{x+y}+ \frac{xy}{y+x}= \frac{(3 x^{2} -xy)(x+y)-(2 x^{2} +y ^{2})(x-y)+xy(x-y) }{(x-y)(x+y)}= \\ = \frac{3 x^{3}- x^{2} y+3 x^{2}y -xy ^{2} -2 x^{3}-xy ^{2}+2 x^{2} y+y ^{3} + x^{2} y-xy ^{2} } {(x-y)(x+y)}= \\ = \frac{ x^{3}+y ^{3}-3xy ^{2} +6 x^{2} y } {(x-y)(x+y)},$ $2) \frac{a ^{3 }+b ^{3} }{a+b}+ \frac{3a ^{2}b}{a+b}+ \frac{3ab ^{2} }{a+b}= \frac{a ^{3 }+b ^{3}+3a ^{2}b+3ab ^{2}}{a+b}=(a+b)^{2}$
$3) \frac{c^{2} }{d-c}- \frac{2cd-d ^{2} }{d-c} = \frac{ c^{2}-2cd+d ^{2} }{(d-c)}= \frac{(d-c)^{2} }{(d-c)}=d-c$