## anonymous one year ago 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

1. SolomonZelman

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

2. SolomonZelman

$$\large\color{black}{ \displaystyle a_n=a_1\times{\rm r}^{n-1} }$$ 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. $$\large\color{black}{ \displaystyle 114688=7\times{\rm r}^{7} }$$

3. SolomonZelman

can you fsolve for common ratio (r) ?

4. SolomonZelman

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

5. SolomonZelman

with a mute*