当x=0时,等式不成立,所以x≠0
等式两边除以x得：x+1/x=3
x^3+1/(x^3)=(x+1/x)(x^2-1+1/x^2)
=(x+1/x)(x^2-1+1/x^2+2-2)
=(x+1/x）[(x+1/x)^2-3]
=3×[3^2-3]
=18