化简求值 [(x+2y)(x-2y)-(2x-y)ˆ2+(3x+y)(2x+5y)]÷(-1/2x),其中x=
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化简求值 [(x+2y)(x-2y)-(2x-y)ˆ2+(3x+y)(2x+5y)]÷(-1/2x),其中x=3,y=1.
=[x^2-4y^2-2x^2+4xy-y^2+6x^2+17xy+5y^2]*(-2x)
=[5x^2+21xy]*(-2x)
=-2x^2(5x+21y)
=-18*36
=-648
再问: 不对吧
再答: =[x^2-4y^2-4x^2+4xy-y^2+6x^2+17xy+5y^2]*(-2x) =[3x^2+21xy]*(-2x) =-2x^2(3x+21y) =-6x^2(x+7y) =-6*9*10 =-540 (sorry)
=[5x^2+21xy]*(-2x)
=-2x^2(5x+21y)
=-18*36
=-648
再问: 不对吧
再答: =[x^2-4y^2-4x^2+4xy-y^2+6x^2+17xy+5y^2]*(-2x) =[3x^2+21xy]*(-2x) =-2x^2(3x+21y) =-6x^2(x+7y) =-6*9*10 =-540 (sorry)
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