Answer
$ a_{n}=16(\dfrac{1}{4})^{n-1}$ and $ a_{12}=\dfrac{1}{(4)^9} =\dfrac{1}{262144}$
Work Step by Step
Here, $ a_1=16$ and $ d=\dfrac{1}{4}$
$ a_{n}=16(\dfrac{1}{4})^{n-1}$
Now, plug in: $ n=12$
$ a_{12}=16(\dfrac{1}{4})^{12-1}$
and $ a_{12}=\dfrac{1}{(4)^9} =\dfrac{1}{262144}$
So, $ a_{n}=16(\dfrac{1}{4})^{n-1}$ and $ a_{12}=\dfrac{1}{(4)^9} =\dfrac{1}{262144}$
