Question

(x+y)(x的平方-xy+y的平方）-(x-y)(x的平方+xy+y的平方）等于多少？

Answer 1

(x+y)(x²-xy+y²）-(x-y)(x²+xy+y²）＝x³+y³－﹙x³－y³﹚＝2x³

Answer 2

原式=2y(x²+y²-xy),关键在于将（x²+y²）看成整体

Answer 3

原式=(x^3+y^3)-(x^3-y^3)
=2y^3