已知n为正整数,且(xn)2 =9,求(1/3x3n)2-3(x2)2n的值.

问题描述:

已知n为正整数,且(xn2 =9,求(

1
3
x3n)2-3(x22n的值.

∵(xn2 =9,
∴x2n=9,
∴原式=

1
9
(x2n3-3(x2n2
=
1
9
×93-3×92
=-162.