已知m-n=4,mn=-1,求(-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn)的值
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已知m-n=4,mn=-1,求(-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn)的值
已知m-n=4,mn=-1,求(-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn)的值
已知m-n=4,mn=-1,求(-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn)的值
(-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn)
=-2mn+2m+3n-3mn-2n+2m-m-4n-mn
=-6mn+3m-3n
=-6*(-1)+3*4
=18
-2mn+2m+3n-3mn-2n+2m-m-4n-mn
=-6mn+3m-3n
=6+3(m-n)
=6+12
=18
去括号得-2mn+2m+3n-3mn-2n+2m-m-4n-mn,合并同类项得-6mn-3n+3m=18
(-2mn+2m+3n)-(3mn+2n-2m)-(m+4n+mn)=-2mn+2m+3n-3mn-2n+2m-m-4n-mn
=-6mn+3m-3n
...
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(-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*4
=18
收起
去括号,化简得
原式=-6mn+3m-3n
=-6mn+3(m-n)
=6+12
=18
原式=-2mn+2m+3n-3mn-2n+2m-m-4n-mn
=3m-3n-6mn
=3(m-n)-6mn
∵m-n=4 mn=-1
∴3(m-n)-6mn=3*4-6*(-1)=18