Question

Find the sum of an 8-term geometric sequence when the first term is 7 and the last term is 114,688 and select the correct answer below.

152,915
16,384
16,377
152,908

Answer 1

have you seen this: \(\large\color{black}{ \displaystyle a_n=a_1\times{\rm r}^{n-1} }\) ?

Answer 2

\(\large\color{black}{ \displaystyle a_n=a_1\times{\rm r}^{n-1} }\)

your number of terms is 8
\(\large\color{black}{ \displaystyle a_8=a_1\times{\rm r}^{8-1} }\)

for 8th term.
\(\large\color{black}{ \displaystyle a_8=a_1\times{\rm r}^{7} }\)

now plug in 8th term and 1st term to find the common ratio.
\(\large\color{black}{ \displaystyle 114688=7\times{\rm r}^{7} }\)

Answer 3

can you fsolve for common ratio (r) ?

Answer 4

don't be silent.... because i can't "talk to a mute".

Answer 5

with a mute*