For arothmetric sequence: a1 = first term;
an= an-1 + d
a1 = the first term in the sequence
an = the nth term in the sequence
an-1 = the term before the nth term
n = the term number
d = the common difference.
For Geometric Sequence:
an=a1*rn-1
an is the nth term of the sequence.
a1 is the first term in the sequence.
r is the common ratio for the geometric sequence. You will either be given this value or be given enough information to compute it. You must substitute a value for r into the formula.
n is treated like the variable in a sequence. For example, when writing the general explicit formula, n is the variable and does not take on a value. But if you want to find the 12th term, then n does take on a value and it would be 12.
