if a1=5 and an=nan-1+2 then find the value of a4 (Please)

Question

I'm stuck on this question!

Answer 1

a1 = 5

an = a1 + d(n-1) = 5+ d(n-1

a4 = 5 + d(4-1) = 5 +3d

a4 = 3d +5, where d= the common difference, if this is an arithmetic sequence. if a4 =22 (see below) thn 3d+5=22

3d = 17 and d = 17/3. But more likely the following is true, where the sequence is not arithmetic or geometric

an = nan-1 + 2 is a little confusing

it probably indicates a recursive formula where

a1 = 1a0 + 2

a2 = 2a1 + 2 = 2(5)+2 = 10+2 =12

a3 = 3a1 +2 = 3(5)+2 = 17

a4 = 4a1 +2 = 4(5) +2 = 22

a4 = 22