Answer:
Sn = -9(1-(-3)^n)/4
Step-by-step explanation:
Since r < 1, the sum of nth term of a geometric sequence is expressed as;
Sn = a(1-r^n)/1-r
a is the first term
n is the number f terms
r is the common ratio
An = -9(1-(-3)^n)/1-(-3)
Sn = -9(1-(-3)^n)/4
Hence the sum of the nth term of the series is Sn = -9(1-(-3)^n)/4
