m²+2n²-6m+8n+17=0
(m²-6m+9)+2(n²+4n+4)=0
(m-3)²+2(n+2)²=0
m-3=0,n+2=0
m=3,n=-2
(2m-n)²-(3n-m)
=(6+2)²-(-6-3)
=64+9
=73