# How do you solve 3x^2 - 123 = 0?

Jun 5, 2016

x=±sqrt41

#### Explanation:

The first step is to take out a common factor of 3.

$3 {x}^{2} - 123 = 0 \Rightarrow 3 \left({x}^{2} - 41\right) = 0$

now ${x}^{2} - 41 = 0 \Rightarrow {x}^{2} = 41$

Taking the 'square root' of both sides

rArrsqrt(x^2)=±sqrt41rArrx=±sqrt41

Jun 5, 2016

$x = \pm \sqrt{41}$

#### Explanation:

Isolate $x$ to find its value

color(blue)(3x^2-123=0

Add $123$ both sides

$\rightarrow 3 {x}^{2} - 123 + 123 = 0 + 123$

$\rightarrow 3 {x}^{2} = 123$

Divide both sides by $3$

$\rightarrow \frac{\cancel{3} {x}^{2}}{\cancel{3}} = \frac{123}{3}$

$\rightarrow {x}^{2} = 41$

Take the square root of both sides

And also remember that,when taking the square root of a number,it can be a positive or negative number

Positive or negative - $\pm$

$\rightarrow \sqrt{{x}^{2}} = \pm \sqrt{41}$

color(green)(rArrx=+-sqrt41