m/x+3 -n/x-3=8x/x的平方-9
[m(x-3)-n(x+3)]/(x+3)(x-3)=8x/(x²-9)
[m(x-3)-n(x+3)]/(x²-9)=8x/(x²-9)
m(x-3)-n(x+3)=8x
(m-n)x-3(m+n)=8x
m-n=8
m+n=0
m=4 n=-4
mn=-16