已知m-n=4,mn=2,求多项式(-2mn+2m+3n)-(3mn+2n-2n)-(m+4n+mn)的值

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已知m-n=4,mn=2,求多项式(-2mn+2m+3n)-(3mn+2n-2n)-(m+4n+mn)的值
已知m-n=4,mn=2,求多项式(-2mn+2m+3n)-(3mn+2n-2n)-(m+4n+mn)的值

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

(-2mn+2m+3n)-(3mn+2n-2n)-(m+4n+mn)
=-2mn+2m+3n-3mn-2n+2n-m-4n-mn
=-6mn+m-n
把m-n=4,mn=2代入上式:
原式=-6×2+4
=-8