Question

x^3+y^3和x^3-y^3等于多少??

还有,(x+y)^3和(x-y)^3等于多少??

Answer 1

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

Answer 2

x^3+y^3=（x+y）（x^2-xy+y^2）
x^3-y^3=(x-y)(x^2+xy+y^2)
(x+y)^3=(x+y)(x^2+2xy+y^2)=x^3+2yx^2+xy^2+yx^2+2xy^2+y^3=x^3+3xy^2+3x^2y+y^3
(x-y)^3=(x-y)(x^2-2xy+y^2)=x^3-3x^2y+3xy^2+y^3