(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y)要详细~ 5
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(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y)
=(x-2y)[(x-y)+(x-3y)]-2(x-3y)(x-4y)
=(x-2y)(2x-4y)-2(x-3y)(x-4y)
=2[(x-2y)^2-(x-3y)(x-4y)]
=2(x^2-4xy+4y^2-x^2+7xy-12y^2)
=2(3xy-8y^2)
=2y(3x-8y)
=(x-2y)[(x-y)+(x-3y)]-2(x-3y)(x-4y)
=(x-2y)(2x-4y)-2(x-3y)(x-4y)
=2[(x-2y)^2-(x-3y)(x-4y)]
=2(x^2-4xy+4y^2-x^2+7xy-12y^2)
=2(3xy-8y^2)
=2y(3x-8y)
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2012-08-18
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x^2-xy-2xy+2y^2+x^2-2xy-3xy+6y^2-2x^2+6xy+4xy-24y^2
=2xy-16y^2
=2xy-16y^2
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