Which recursive formula represents the sequence −15, −12, −9,

Question

an=3n−18
A sub n is equal to 3 n minus 18

an=an−1−3; a1=−15
an=an−1−3; a1=−15

an=an−1−15; a1=3
an=an−1−15; a1=3

an=an−1+3; a1=−15

Answer 1

redundant repetition is so annoying.
clearly
a1 = -15
and each successive term is 3 more than the last.
so, which choice reflects that fact?