Find the 9th Term -8 , -24 , -72 , -216 , -648 , -1944 , -5832 , -17496

This is a geometric sequence since there is a common ratio between each term. In this case, multiplying the previous term in the sequence by ${\displaystyle 3}$ gives the next term. In other words, ${\displaystyle a_n=a_1{r}^{n-1}}$.

This is the form of a geometric sequence.

Substitute in the values of ${\displaystyle a_1=-8}$ and ${\displaystyle r=3}$.

Substitute in the value of ${\displaystyle n}$ to find the ${\displaystyle n}$th term.

Subtract ${\displaystyle 1}$ from ${\displaystyle 9}$.

Raise ${\displaystyle 3}$ to the power of ${\displaystyle 8}$.