已知m-n=4,mn=2,求多项式（-2mn+2m+3n)-(3mn+2n-2n)-(m+4n+mn)的值
问题描述：
已知m-n=4,mn=2,求多项式（-2mn+2m+3n)-(3mn+2n-2n)-(m+4n+mn)的值
答
原式=-2mn+2m+3n-3mn-2n+2n-m-4n-mn
=-6mn+m-n
=-6×2+4
=-8