Chapter 12.3, Problem 19AYU

To determine

To find: The fifth term and $nth$ term of the geometric sequence.

Answer to Problem 19AYU

The fifth term of the geometric sequence is $5$ and the $nth$ term is $\left(5\right){\left(-1\right)}^{n-1}$ .

Explanation of Solution

Given information:

The first term $a_1=5$ and the common ratio $r=-1$ .

Calculation:

The formula for nth term of geometric sequence is given by,

  $a_n=a_1{r}^{n-1}$

Calculate the fifth term.

  $\begin{array}{c}{a}_n=\left(5\right){\left(-1\right)}^{5-1}\\ =\left(5\right){\left(-1\right)}^4\\ =5\end{array}$

Calculate the $nth$ term.

  $a_n=\left(5\right){\left(-1\right)}^{n-1}$

Therefore, the fifth term of the geometric sequence is $5$ and the $nth$ term is $\left(5\right){\left(-1\right)}^{n-1}$ .