R=-2 s7=86 and a1=2 find a7 for the geometric series

A geometric series is one where each term is obtained by multiplying a non-zero number, known as the common ratio, r.

Using the formula for the nth term of a geometric series which is an=a1r^ (n-1), we find that a7=-128. This is done by substituting values of a1=2, r=-2, and n=7.