题目内容
【题目】若多项式2(x2-xy-3y2)-(3x2-axy+y2)中不含xy项,则a=____,化简结果为_____.
【答案】 2 -x2-7y2
【解析】2(x2-xy-3y2)-(3x2-axy+y2)
=2x2-2xy-6y2-3x2+axy+y2
=-x2+(a-2)xy-5y2
由题意得
a-2=0,
∴a=2,
∴原式=-x2+(2-2)xy-5y2=-x2-5y2.
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题目内容
【题目】若多项式2(x2-xy-3y2)-(3x2-axy+y2)中不含xy项,则a=____,化简结果为_____.
【答案】 2 -x2-7y2
【解析】2(x2-xy-3y2)-(3x2-axy+y2)
=2x2-2xy-6y2-3x2+axy+y2
=-x2+(a-2)xy-5y2
由题意得
a-2=0,
∴a=2,
∴原式=-x2+(2-2)xy-5y2=-x2-5y2.