已知数列an是公差不为零的等差数列a1=1且a1a2a6成等比数列 求通项公式

Question

如题所述

Answer 1

a1a2a6成等比数列
a2 ^2 =a1a6
(a1+d)^2=a1(a1+5d)
a1^2+2a1d+d^2=a1^2+5a1d
3a1d=d^2
d=3
通项公式
an=a1+(n-1)d
=1+3n-3
=3n-2