要使多项式2mxy-xy+1-2x2-4mxy+5x2+7xy中不含xy项，则m的值为______．
人气：217 ℃ 时间：2019-08-19 16:49:35
解答
2mxy-xy+1-2x2-4mxy+5x2+7xy
=5x2-2x2-4mxy+7xy+2mxy-xy+1
=3x2+（-4m+7+2m-1）xy+1，
因为没有xy项，
所以-4m+7+2m-1=0，
解得m=3．
故答案为：3．
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