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-(2x^20-7xy)-2[2x^2-(3x^2-5xy+y^2)]化简
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-(2x^20-7xy)-2[2x^2-(3x^2-5xy+y^2)]化简
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答案和解析
第一项错了吧,是平方
-(2x^2-7xy)-2[2x^2-(3x^2-5xy+y^2)]
=-2x^2+7xy-4x^2+2(3x^2-5xy+y^2)
=-6x^2+7xy+6x^2-10xy+2y^2
=-3xy-10xy+2y^2
-(2x^2-7xy)-2[2x^2-(3x^2-5xy+y^2)]
=-2x^2+7xy-4x^2+2(3x^2-5xy+y^2)
=-6x^2+7xy+6x^2-10xy+2y^2
=-3xy-10xy+2y^2
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