已知(m-2)^2+|2m-n|=0,求m^2-mn+2n^2的值,
问题描述：
已知(m-2)^2+|2m-n|=0,求m^2-mn+2n^2的值,
答
∵(m-2)²+|2m-n|=0
∴m-2=0,2m-n=0
∴m=2,n=4
∴m²-mn+2n²
=2²-2×4+2×4²
=4-8+32
=28