We have the arithmetic sequence of 18, 12, 6 , 0
Firstly, let us find the common difference
from the sequence
12 - 18 = -6
6 - 12 = -6
0-6 = -6
Therefore, the common difference for the sequence is -6
The recursive formula is an + 1 = an + d
an is the number of term
an + 1 = an + (-6)
an + 1 = an - 6
The answer is
an + 1 = an - 6