135=x^2-4

Solution for 135=x^2-4 equation:

135=x^2-4

We move all terms to the left:

135-(x^2-4)=0

We get rid of parentheses

-x^2+4+135=0

We add all the numbers together, and all the variables

-1x^2+139=0

a = -1; b = 0; c = +139;
Δ = b2-4ac
Δ = 02-4·(-1)·139
Δ = 556
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:

$\sqrt{\Delta}=\sqrt{556}=\sqrt{4*139}=\sqrt{4}*\sqrt{139}=2\sqrt{139}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-2\sqrt{139}}{2*-1}=\frac{0-2\sqrt{139}}{-2}
=-\frac{2\sqrt{139}}{-2}
=-\frac{\sqrt{139}}{-1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+2\sqrt{139}}{2*-1}=\frac{0+2\sqrt{139}}{-2}
=\frac{2\sqrt{139}}{-2}
=\frac{\sqrt{139}}{-1}
$