Mathematics
OpenStudy (anonymous):

find a(n) for the following geometric sequence a(1)=3,r=-3

OpenStudy (anonymous):

a(n) = 3*(-3)^(n-1)

OpenStudy (anonymous):

3/4 1/(1-(-3)) or sum of $\sum_{1}^{\infty}1(-3)^n$ don't know what you are looking for