Solve Using the Square Root Property 5(x+4)^2=90

$5 {(x + 4)}^{2} = 90$

Step 1

Divide each term in $5 {(x + 4)}^{2} = 90$ by $5$ and simplify.

Divide each term in $5 {(x + 4)}^{2} = 90$ by $5$ .

$\frac{5 {(x + 4)}^{2}}{5} = \frac{90}{5}$

Simplify the left side.

Cancel the common factor of $5$ .

Cancel the common factor.

$\frac{5 {(x + 4)}^{2}}{5} = \frac{90}{5}$

Divide ${(x + 4)}^{2}$ by $1$ .

${(x + 4)}^{2} = \frac{90}{5}$

Simplify the right side.

Divide $90$ by $5$ .

${(x + 4)}^{2} = 18$

Step 2

Take the specified root of both sides of the equation to eliminate the exponent on the left side.

$x + 4 = \pm \sqrt{18}$

Step 3

Simplify $\pm \sqrt{18}$ .

Rewrite $18$ as $3^{2} \cdot 2$ .

Factor $9$ out of $18$ .

$x + 4 = \pm \sqrt{9 (2)}$

Rewrite $9$ as $3^{2}$ .

$x + 4 = \pm \sqrt{3^{2} \cdot 2}$

Pull terms out from under the radical.

$x + 4 = \pm 3 \sqrt{2}$

Step 4

The complete solution is the result of both the positive and negative portions of the solution.

First, use the positive value of the $\pm$ to find the first solution.

$x + 4 = 3 \sqrt{2}$

Subtract $4$ from both sides of the equation.

$x = 3 \sqrt{2} - 4$

Next, use the negative value of the $\pm$ to find the second solution.

$x + 4 = - 3 \sqrt{2}$

Subtract $4$ from both sides of the equation.

$x = - 3 \sqrt{2} - 4$

The complete solution is the result of both the positive and negative portions of the solution.

$x = 3 \sqrt{2} - 4, - 3 \sqrt{2} - 4$

Step 5

The result can be shown in multiple forms.

Exact Form:

$x = 3 \sqrt{2} - 4, - 3 \sqrt{2} - 4$

Decimal Form:

$x = 0.24264068 \dots, - 8.24264068 \dots$