第三题的第二小题怎么做？数学学霸帮帮忙 5
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x(y-3)-(2y-6)
=x(y-3)-2(y-3)
=(y-3)(y-2)
(x+y)^3-(x-y)^2(x+y)
=(x+y)[(x+y)^2-(x-y)^2]
=(x+y)[(x+y+x-y)(x+y-x+y)]
=(x+y)*2x*2y
=4xy(x+y)
x(x^2-xy)-(4x^2-4xy)
=x^2(x-y)-4x(x-y)
=x(x-y)(x-4)
=x(y-3)-2(y-3)
=(y-3)(y-2)
(x+y)^3-(x-y)^2(x+y)
=(x+y)[(x+y)^2-(x-y)^2]
=(x+y)[(x+y+x-y)(x+y-x+y)]
=(x+y)*2x*2y
=4xy(x+y)
x(x^2-xy)-(4x^2-4xy)
=x^2(x-y)-4x(x-y)
=x(x-y)(x-4)
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