I am also stuck on this question. Let {b sub k} be a geometric sequence. Given that (b sub 4)= 80, (b sub 9)=1280, and (S sub 9)=2555. Find the first term (b sub 1).

I have tried it every way I know how but I am getting nowhere. No amount of searching on the internet has helped either. Thanks!!!

Picture of problem:

I have tried it every way I know how but I am getting nowhere. No amount of searching on the internet has helped either. Thanks!!!

Picture of problem:

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