Answer
$ a_{n}=0.0007(-10)^{n-1}$ and $ a_{7}=700$
Work Step by Step
The general formula to find the nth term of a Geometric sequence is given as: $ a_{n}=a_1r^{n-1}$
$ r=\dfrac{a_2}{a_1}=\dfrac{-0.007}{0.0007}=-10$ and $ n=7$
Now, $ a_{n}=0.0007(-10)^{n-1}$
Now, $ a_{7}=0.0007(-10)^{7-1}=700$
Our answers are: $ a_{n}=0.0007(-10)^{n-1}$ and $ a_{7}=700$
