Question

find the sum of a 9-term geometric sequence when the first term is 4 and the last term is 1,024 and select the correct answer below. 682 2,044 2,048 678

Answer 1

Hello,


`u_(1) =4\\ u_(2) =4*q\\ u_(3) =4*q^2\\ ...\\ u_(9) =4*q^8\\\\ ==\textgreater\ 4*q^8=1024\\ ==\textgreater\ q^8=256\\ ==\textgreater\ q=2\mbox{( and there is a problem in the question) } \ or \ q=-2\\ if\ q=2 \ then\ \sum_(i=0)^(8)\ 4*(2)^i= 4*(1-2^9)/(1-2) =2044\\ if \ q=-2 \ then\ \sum_(i=0)^(8)\ 4*(-2)^i= 4*(1-(-2)^9)/(1+2) =684\\`

Answer B (but see the problem)

Answer 2

I just did the test and the answer was 2,044.

Explanation:

I Promise just trust me