2x^1-(3m+n)x+mn=0,m>n>0
x1
=[3m+n+√（n^2-2mn+9m^2)]/4
={3m+n+√[（n-m)^2+8m^2]}/4
>(3m+n+2√2m)/4
>(3n+n+2√2n)/4
=n+√2n/2
>n
x2
=[3m+n-√（n^2-2mn+9m^2)]/4