Question

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

Answer 1

`+-sqrt(22)`

Explanation:

Subtract `3` to the other side

`-4x^2 = -88`

Then, divide both sides by `-4`

`x^2 = 22`

Finally, take the square root of both sides.

`x = +-sqrt(22)`

Answer 2

Rearrange the expression and you will find that `x=+-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)-4x^2color(red)(cancel(-3))=-85color(red)(-3)`

`-4x^2=-88`

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

`(cancel(-4)x^2)/color(red)(cancel(-4))=(cancel(-)88)/color(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 `+-` in because both positive and negative values yield positive answers when squared.