Find the Fourth Term 128 , 32 , 8

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 ${\displaystyle \frac{1}{4}}$ gives the next term. In other words, ${\displaystyle a_n=a_1{r}^{n-1}}$.

Geometric Sequence: ${\displaystyle r=\frac{1}{4}}$

This is the form of a geometric sequence.

Substitute in the values of ${\displaystyle a_1=128}$ and ${\displaystyle r=\frac{1}{4}}$.

Apply the product rule to ${\displaystyle \frac{1}{4}}$.

One to any power is one.

Combine ${\displaystyle 128}$ and ${\displaystyle \frac{1}{4^{n-1}}}$.

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