Question

Given that first term of an AP is 2and common difference was 8 and S_n was 90,find n and a_n

Answer 1

Since

An=a+(n-1)d

An=2+(n-1)8

=2+(8n-8)

=

Answer 2

An = 8n - 6

Sn = 90

since the terms are 2,10,18,26,34 = 90

therefore n = 5