Solve Using the Square Root Property 3x^2-7=-55

$3 x^{2} - 7 = - 55$

Step 1

Move all terms not containing $x$ to the right side of the equation.

Add $7$ to both sides of the equation.

$3 x^{2} = - 55 + 7$

Add $- 55$ and $7$ .

$3 x^{2} = - 48$

Step 2

Divide each term in $3 x^{2} = - 48$ by $3$ and simplify.

Divide each term in $3 x^{2} = - 48$ by $3$ .

$\frac{3 x^{2}}{3} = \frac{- 48}{3}$

Simplify the left side.

Cancel the common factor of $3$ .

Cancel the common factor.

$\frac{3 x^{2}}{3} = \frac{- 48}{3}$

Divide $x^{2}$ by $1$ .

$x^{2} = \frac{- 48}{3}$

Simplify the right side.

Divide $- 48$ by $3$ .

$x^{2} = - 16$

Step 3

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

$x = \pm \sqrt{- 16}$

Step 4

Simplify $\pm \sqrt{- 16}$ .

Rewrite $- 16$ as $- 1 (16)$ .

$x = \pm \sqrt{- 1 (16)}$

Rewrite $\sqrt{- 1 (16)}$ as $\sqrt{- 1} \cdot \sqrt{16}$ .

$x = \pm \sqrt{- 1} \cdot \sqrt{16}$

Rewrite $\sqrt{- 1}$ as $i$ .

$x = \pm i \cdot \sqrt{16}$

Rewrite $16$ as $4^{2}$ .

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

Pull terms out from under the radical, assuming positive real numbers.

$x = \pm i \cdot 4$

Move $4$ to the left of $i$ .

$x = \pm 4 i$

Step 5

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.

$x = 4 i$

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

$x = - 4 i$

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

$x = 4 i, - 4 i$