x^2n+3-x^2n+2+x^2n+1
问题描述:
x^2n+3-x^2n+2+x^2n+1
答
x^2n+3-x^2n+2+x^2n+1
=(x^2n-x^2n+x^2n)+3+2+1
=x^2n+6.