Question

What is the sum of the geometric sequence 1, -4, 16, ... if there are 7 terms?
Choose one answer.
a. -5,461
b. 5,461
c. -3,277
d. 3,277

Answer 1

Sum of GS \(\large = \frac{a(1-r^n)}{1-r}\)
Now, a=1 , r=-4/1 = -4 , n=7
Sum of GS \(\large = \frac{(1)(1-(-4)^7)}{1-(-4)} = ...?\)