determine the sum of the geometric series 7+35+75+...+t8
The sequence should be
7,35,175, ....... , t8
As common ratio is 5
So S8
That is 7+35+175+........+t8
We have
a=7
r=5
n=8
Use "S_n=a_1.\\frac{1-r^n}{1-r}=7.\\frac{1-5^8}{1-5}"
"\\boxed{S_n=683592}answer"
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