已知:x+y+z=0,求证"x^3+y^3+z^3=3xyz

来源:学生作业帮助网 编辑:六六作业网 时间:2024/12/19 05:57:32
已知:x+y+z=0,求证"x^3+y^3+z^3=3xyz已知:x+y+z=0,求证"x^3+y^3+z^3=3xyz已知:x+y+z=0,求证"x^3+y^3+z^3=3xyzx^3+y^3+z^

已知:x+y+z=0,求证"x^3+y^3+z^3=3xyz
已知:x+y+z=0,求证"x^3+y^3+z^3=3xyz

已知:x+y+z=0,求证"x^3+y^3+z^3=3xyz
x^3+y^3+z^3=3xyz
x^3+y^3+z^3-3xyz=0
(x+y+z)(x^2+y^2+z^2-xy-yz-xz)
因为x+y+z=0,
所以x^3+y^3+z^3-3xyz=0
x^3+y^3+z^3=3xyz

根据http://zhidao.baidu.com/question/6851206.html?fr=qrl3的分解因式
x^3+y^3+z^3-3xyz=(x+y+z)(x^2+y^2+z^2-xy-yz-zx)
由x^3+y^3+z^3=(x+y+z)(x^2+y^2+z^2)-z(x^2+y^2)-x(y^2+z^2)-y(x^2+z^2)
x^3+y^3+z^3-3xyz=……=(x+y+z)(x^2+y^2+z^2-xy-yz-zx) =0
故x^3+y^3+z^3=3xyz