已知n為正整數,且(xn)2 =9,求(13x3n)2-3(x2)2n的值.

已知n為正整數,且(xn)2 =9,求(13x3n)2-3(x2)2n的值.

∵(xn)2 =9,∴x2n=9,∴原式=19(x2n)3-3(x2n)2=19×93-3×92=-162.