（3/4a^n+1-1/2b^n)*2ab-(2/3a^n+1-5/6b^n)*3ab
问题描述：
（3/4a^n+1-1/2b^n)*2ab-(2/3a^n+1-5/6b^n)*3ab
n+1和n都是指数
答
=[(6/4a^n+1)-1/b^n-(3/3a^n+1)+5/2b^n]*ab
=[(18a^n+6-12a^n-3)/(4^an+1)*(3a^n+1)+3/2b^n]*ab
=[(6a^n+3)/(4a^n+1)*(3a^n+1)+3/2b^n]*ab