Question

What is the sum of an 8 term geometric sequence if the first term is -11, the last term is 180,224 and the common ratio is -4
-143,231
-36,047
144,177
716,144

Answer 1

Answer:

3rd option

Step-by-step explanation:

The sum of n terms of a geometric sequence is

$S_{n}$ = $\frac{a_{1}(r^{n}-1) }{r-1}$

where a₁ is the first term and r the common ratio

Here a₁ = - 11 and r = - 4 , then

S₈ = $\frac{-11(-4)^{8}-1) }{-4-1}$

   = $\frac{-11(65536-1)}{-5}$

   = $\frac{-11(65535)}{-5}$

   = $\frac{-720885}{-5}$

   = 144177