3x^2-9=121

Solution for 3x^2-9=121 equation:

3x^2-9=121

We move all terms to the left:

3x^2-9-(121)=0

We add all the numbers together, and all the variables

3x^2-130=0

a = 3; b = 0; c = -130;
Δ = b2-4ac
Δ = 02-4·3·(-130)
Δ = 1560
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{1560}=\sqrt{4*390}=\sqrt{4}*\sqrt{390}=2\sqrt{390}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-2\sqrt{390}}{2*3}=\frac{0-2\sqrt{390}}{6}
=-\frac{2\sqrt{390}}{6}
=-\frac{\sqrt{390}}{3}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+2\sqrt{390}}{2*3}=\frac{0+2\sqrt{390}}{6}
=\frac{2\sqrt{390}}{6}
=\frac{\sqrt{390}}{3}
$