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问题: 因式分解的题

1. 当x-y=1时, x^4-xy^3-x^3y-3x^2y+3xy^2+y^4是多少

解答:

x^4-xy^3-x^3y-3x^2y+3xy^2+y^4
= x^3(x-y)-y^3(x-y)-3xy(x-y) = x^3-y^3-3xy
= (x-y)(x^2+xy+y^2)-3xy = x^2+xy+y^2-3xy
= (x-y)^2
= 0