Find the 87th term of the arithmetic sequence 12, 0, -12

a(87) = -590

Step-by-step explanation:

Notice how each term of this arithmetic sequence is equal to the sum of the previous term and the common difference, -12.

The general formula a(n) = a(1) + (n - 1)d becomes:

                                    a(n) = 12 - 7(n - 1)

and the 87th term        a(87) = 12 - 7(87 - 1), or

                                      a(87) = 12 - 7(86)

                                       a(87) = -590

-2

7 - 9 = -2

reversed:

-2 + 9 = 7