解
x+1/x=5/2
两边平方得:
x²+2+1/x²=25/4
∴
x²+1/x²=25/4-2=17/4
∴x³+(1/x)³
=(x+1/x)(x²-1+1/x²)
=5/2×(17/4-1)
=5/2×(13/4)
=65/8