Answer: - 9, - 3, 3, 9, 15, 21
Explanation:
The given formula is
an = a(n - 1) + 6
a1 = - 9
where
n, n - 1 and 1 are subscripts
This is a recursive formula. Each term is defined with respect to the term before it.
From the information given,
first term = a1 = - 9
Second term = a2 = a(2 - 1) + 6 = a1 + 6 = - 9 + 6
a2 = - 3
Third term = a3 = a(3 - 1) + 6 = a2 + 6 = - 3 + 6
a3 = 3
Fourth term = a4 = a(4 - 1) + 6 = a3 + 6 = 3 + 6
a4 = 9
Fifth term = a5 = a(5 - 1) + 6 = a4 + 6 = 9 + 6
a5 = 15
Sixth term = a6 = a(6 - 1) + 6 = a5 + 6 = 15 + 6
a6 = 21
Thus, the first six terms are
- 9, - 3, 3, 9, 15, 21
