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How do you find the common ratio, r, for the geometric sequence that has a1 =100 and a8 = ?

1 Answer

Nov 8, 2015

$r = \sqrt[7]{\frac{a_{8}}{a_{1}}}$ $r=root(7)(a_8/a_1)$

See explanation.

Explanation:

The task is incomplete, because the term $a_{8}$ $a_8$ is missing, but it is possible to show the way to solve the task.

According to the $n - t h$ $n-th$ term formula we can write, that:

$a_{8} = a_{1} \cdot r^{7}$ $a_8=a_1*r^7$ , so

$r^{7} = \frac{a_{8}}{a_{1}}$ $r^7=a_8/a_1$

$r = \sqrt[7]{\frac{a_{8}}{a_{1}}}$ $r=root(7)(a_8/a_1)$

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