已知m-n=3,mn=-1,求多项式-2mn+2m+3n-3mn-2n+2m-4n-m-mn的值

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已知m-n=3,mn=-1,求多项式-2mn+2m+3n-3mn-2n+2m-4n-m-mn的值

已知m-n=3,mn=-1,求多项式-2mn+2m+3n-3mn-2n+2m-4n-m-mn的值
已知m-n=3,mn=-1,求多项式-2mn+2m+3n-3mn-2n+2m-4n-m-mn的值

已知m-n=3,mn=-1,求多项式-2mn+2m+3n-3mn-2n+2m-4n-m-mn的值
-2mn+2m+3n-3mn-2n+2m-4n-m-mn
=-6mn+3m-3n
=-6mn+3(m-n)
=6+9
=15

15 先合并同类项

-2mn+2m+3n-3mn-2n+2m-4n-m-mn
=-6mn+3m-3n
=-6mn+3(m-n)
=-6*(-1)+3*3
=6+9
=15