m^2+n^2-10m+6n+34=0
(m^2-10m+25)+(n^2+6n+9)=0
(m-5)^2+(n+3)^2=0
根据一个数的平方必然大于或者等于0
所以m-5=0 n+3=0
m=5,n=-3
2m+5n=10-15=-5