Find the fourth term of an arithmetic sequence if the first term is 12 and the common difference is -3.

Question

a₄ =

Answer 1

a_{n =} a₁ + (n - 1) d

a_n = 12 + (n - 1)( -3) = 12 -3n + 3 = 15 - 3n

a₄ = 15 - 3 • 4 = 15 -12 =3

Fourth term = 3

12 , 9 , 6 , 3

Answer 2

See solutions to previous posts and use formula.