八年级数学 分式当实数m,n满足代数式x-1分之m,加x+2分之n,等于（x-1）（x+2)分之2x+7时,求m,n的值

m/(x-1)+n/(x+2)=(2x+7)/(x-1)(x+2)
m(x+2)+n(x-1)=2x+7
(m+n)x+2m-n=2x+7
m+n=2
2m-n=7
3m=9
m=3
3+n=2
n=-1