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问题: 数学计算题

(x²+xy-y²)(x²+xy+y²)-x²(x+y)²

解答:

(x²+xy-y²)(x²+xy+y²)-x²(x+y)²
=(x^2+xy)^2-y^4-x^2(x^2+2xy+y^2)
=x^4+2x^3y+x^2y^2-y^4-x^4-2x^3y-x^2y^2
=-y^4