若n为正整数,则化简(-1)^2n*a+(-1)^2n+1*a
问题描述：
若n为正整数,则化简(-1)^2n*a+(-1)^2n+1*a
答
n为正整数,则2n是偶数,2n+1是奇数.
(-1)^2n*a+(-1)^2n+1*a
=1*a-1+1*a
=2a-1