在公差不为零的等差数列an中,a1.a3.a7依次成等比数列,前7项和为35,则数列an的通项an等于?

设等差数列的公差为d(d≠0)a1.a3.a7依次成等比数列∴ a3²=a1*a7∴ (a1+2d)²=a1(a1+6d)∴ 4d²=2a1d∵ d≠0∴ a1=2d∴ an=a1+(n-1)d=(n+1)d∴ S7=(a1+a7)*7/2=(2d+8d)*7/2=35d=35∴ d=1∴ an=n+1...