Given an arithmetic sequence with a thirteenth term, a13 = −111, and a common difference, d = 11, find the 5th term: a5 = ?

Question

a₅ = −199

a₅ = −210

a₅ = −188

a₅ = −221

Answer 1

Start by finding A(1)

A(13) = A(1) + 9(n-1)

-111 = A(1) +(9 x12)

-111 = A(1) =108

A(1)= -219

So now A(5) = A(1) +9(4)

A(5) = -219 +36

A(5) = -183