(根号x^3+1/x^3-y)+(x+1/x-3)^2=0,
x^3+(1/x)^3=y
x+1/x=3
则x^2+1/x^2=3^2-2=7
y=x^3+(1/x)^3
=(x+1/x)(x^2-1+1/x^2)
=3*6
=18
y的平方根=±3根号2