Question

If f(n) = f( n-1 ) + 7 and f(1) = -18 then f(5) = ?

Answer 1

10

Explanation:

`f_n = f_n_-_1 + 7\\f_1 = -18\\f_2 = -18 + 7 = -11\\f_3 = -11 + 7 = -4\\f_4 = -4 + 7 = 3\\f_5 = 3 + 7 = 10\\`

A faster way is to take the common additive (7) times the difference in n, in this case (5-1 = 4)

`-18 + 7(4)\\-18 + 28\\10`