Write a geometric series if $r = 1/6$ and $n = 8$.

Question

Write a geometric series if $r = 1/6$ and $n = 8$.

I tried using the formula $a_n = a_1r^{n-1}$ and $S_n = a_1\cfrac{(1-r^n)}{1-r}$ but I don't know how to find the values for the terms like $a_1$.

Answer 1

You can take $a_1$ whatever you like and then proceed by multiplying it with the common ratio $\frac 1 6$ successively until you reach at the $8$-th term.