Question

What is the formula for the following arithmetic sequence?

Answer 1

$a_{n}$ = 12 + (- 6)(n - 1 )

This is an arithmetic sequence with n th term

$a_{n}$ = $a_{1}$ + (n - 1)d

here d = - 6 - 0 = 0 - 6 = 6 - 12 = -6 and $a_{1}$ = 12, hence

$a_{n}$ = 12 + (- 6)(n - 1)

use this formula to find the 30 th term

$a_{30}$ = 12 + (- 6 × 29) = 12 - 174 = - 162