一道初中数学代数题
(x+y)^3-(x^3+y^3)/(x+y)
参考答案:x^3+y^3+3x^2y+3xy^2-(x+y)(x^2-xy+y^2)/(x+y)
=x^3+y^3+3x^2y+3xy^2-x^2+xy-y^2
应该把(x+y)^3-(x^3+y^3)整个括起来,就得:
(x+y)^3-(x+y)(x^2+y^2-xy)
——————————————
(x+y)
上下同除(x+y),得(x+y)^2-x^2-y^2+xy
=x^2+y^2+2xy-x^2-y^2+xy
=3xy