m n是正数 0
问题描述：
m n是正数 0
答
[m^2/(1-x)+ n^2/x] - (m+n)^2=m^2/(1-x)+ n^2/x - m^2 -n^2 -2mn=m^2[1/(1-x) -1] +n^2[1/x -1] -2mn=m^2 [x/(1-x)]+n^2[(1-x)/x]-2mn=[m^2 x^2 +n^2(1-x)^2 -2mnx(1-x)]/[x(1-x)] 0= (m+n)^2