m/x+3 - n/x-3 = 8x/x^2-9(x≠±3),则mn

m/x+3 - n/x-3 = 8x/x^2-9(x≠±3),则mn
m/x+3 - n/x-3 = 8x/x^2-9(x≠±3),则mn

m/x+3 - n/x-3 = 8x/x^2-9(x≠±3),则mn
m/x+3 - n/x-3 = 8x/x^2-9(x≠±3)
[m(x-3)-n(x+3)]/(x^2-9）= 8x/(x^2-9)
∴m(x-3)-n(x+3)= 8x
(m-n)x-(3m+3n)=8x
∴m-n=8
3m+3n=0
∴m=4 n=-4
或 m=-4 n=4
∴mn =-16

通分得
[(x-3)*m-(x+3)*n]/x^2-9=8x/x^2-9
(m-n)x-3(m+n)=8x
m-n=8
m+n=0
得
m=4
n=-4
mn=-16

很简单啊！
左边=mx-3m-nx-3n/(x^2-9)=8x/(x^2-9)(通分得到)
所以
m-n=8
3m+3n=0
mn=-16