根据题意
绝对值和完全平方非负
所以mn-1=0
m-n-2=0
mn=1
m-n=2
（-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn)
=-2mn+2m+3n-3mn-2n+2m-m-4n-mn
=-6mn+3m-3n
=-6mn+3(m-n)
=-6×1+3×2
=0