Question

Find the fourth term of the geometric sequence whose first term is 7 and whose common ratio is -3

Answer 1

A GP Is in the form of
a, ar, ar^2....
a= first term
r= common ratio
its nth term is given as
\[a_n=ar^{n-1}\]
We are given first term as a=7
r=-3
We have to find 4th term
\[a_4=7\times (-3)^{(4-1)}\]
\[a_4=7 \times (-3)^3=7\times (-27)=-189\]
so the fourth term is -189