# How do you solve 3-4x^2=-85?

May 8, 2018

$\pm \sqrt{22}$

#### Explanation:

Subtract $3$ to the other side

$- 4 {x}^{2} = - 88$

Then, divide both sides by $- 4$

${x}^{2} = 22$

Finally, take the square root of both sides.

$x = \pm \sqrt{22}$

May 8, 2018

Rearrange the expression and you will find that $x = \pm 4.69$

#### Explanation:

First, we'll rearrange the expression such that all of the constants are on one side of the expression, and all of the terms directly related to $x$ are on the other side:

$\cancel{3} - 4 {x}^{2} \textcolor{red}{\cancel{- 3}} = - 85 \textcolor{red}{- 3}$

$- 4 {x}^{2} = - 88$

Now, we'll divide by the coefficient on $x$'s side:

$\frac{\cancel{- 4} {x}^{2}}{\textcolor{red}{\cancel{- 4}}} = \frac{\cancel{-} 88}{\textcolor{red}{\cancel{-} 4}}$

${x}^{2} = 22$

Finally, we'll take the square root of both sides to get the answer:

$\sqrt{{x}^{2}} = \sqrt{22}$

color(green)(x=+-sqrt(22)=+-4.69

You have to put the $\pm$ in because both positive and negative values yield positive answers when squared.