m+2n=8,mn=30,则m(2-m)+(m+n)*(m-4)=?
人气：453 ℃ 时间：2020-10-01 13:46:02
解答
原式=2m-m^2+m^2-4m+mn-4n
=-2m+mn-4n
=-2(m+2n)+mn
把m+2n=8,mn=30代入-2(m+2n)+mn
得-2*8+30
=-16+30
=14
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