(x+y)²-(x³+y³)÷(x+y)等于?

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(x+y)²-(x³+y³)÷(x+y)等于?

解:
(x+y)^2-(x^3+y^3)/(x+y)
=(x+y)^2-[(x+y)(x^2-xy+y^2)]/(x+y)
=(x+y)^2-[x^2-xy+y^2]
=x^2+y^2+2xy-x^2+xy-y^2
=3xy