The easiest way to answer this is to try all choices, plug
in values for the 1st term and 2nd term then check if the
answer matches with 5 and 2. (n = 1 and n = 2)
We know that n starts with 1 because that is our 1st
term, we do not have 0th term, therefore that leaves us with 2
choices.
Choice 1: an = 5 − 2(n − 1); all integers where n ≥ 1
n = 1
a1 = 5 – 2 (1 – 1) = 5 – 2 (0)
a1 = 5
n = 2
a2 = 5 – 2 (2 – 1) = 5 – 2 (1)
a2 = 3 (FALSE!)
Choice 2: an = 5 − 3(n − 1); all integers where n ≥ 1
n = 1
a1 = 5 – 3 (1 – 1) = 5 – 3 (0)
a1 = 5
n = 2
a2 = 5 – 3 (2 – 1) = 5 – 3 (1)
a2 = 2 (TRUE)
Therefore the correct answer is:
an = 5 − 3(n − 1); all integers where n ≥ 1
