x+y+z=0,z=-（x+y）
代入x^3+y^3+z^3=0
x^3+y^3-(x+y)^3
=x^3+y^3-x^3-3X^2y-3xy^2-y^3
=-3xy(x+y)
=3xyz=0
所以xyz=0
3a²+ab-2b²=(3a-2b)(a+b)=0
得3a=2b或a=-b
所以a/b-b/a-(a^2+b^2)/ab=a/b-b/a-a/b-b/a=-2b/a
当3a=2b时,-2b/a=-3；
当a=-b时,-2b/a=2
即b分之a-a分之b-ab分之a²+b²=-3或2
a²-3a+1=0
2a5-5a4+2a3-8a²+3a=(a²-3a+1)(2a^3+a^2+3a)=0