# How do you solve 4r^2+1=325?

Jan 20, 2017

${r}^{2} = 81$ which means $r$ is either 9 or -9.

#### Explanation:

Given the equation $4 {r}^{2} + 1 = 325$, we are going to look for ${r}^{2}$

So to find ${r}^{2}$ we are going to isolate it on one side of the equation.

Step 1:

Subtract 1 from both sides of the equation

$4 {r}^{2} + 1 - 1 = 325 - 1$

So we get $4 {r}^{2} = 324$

Step 2:

Divide both sides by 4

$4 {r}^{2} / 4 = \frac{324}{4}$

So now we isolated have ${r}^{2}$ isolated

${r}^{2} = 81$

$r = \pm 9$