How do you find $a_{9}$ $a_9$ for the geometric sequence $1/5, 1, 5,...$ ?

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Answer 1 · 2016-10-23T19:53:41

. $a_9=5^7=78125$

The GP $1/5, 1, 5....$

comparing with the standard GP $a, ar, ar^2, ....$

we note the first term

$=1/5$

and the common ratio is $r= 5$

$:. a_n=ar^n-1$

so $a_9=(1/5)5^8$

ie.. $a_9=5^7=78125$

How do you find a_9a9a_9 for the geometric sequence 1/5, 1, 5,...1/5, 1, 5,...?