5=x^2+15x-105

Solution for 5=x^2+15x-105 equation:

5=x^2+15x-105

We move all terms to the left:

5-(x^2+15x-105)=0

We get rid of parentheses

-x^2-15x+105+5=0

We add all the numbers together, and all the variables

-1x^2-15x+110=0

a = -1; b = -15; c = +110;
Δ = b2-4ac
Δ = -152-4·(-1)·110
Δ = 665
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-\sqrt{665}}{2*-1}=\frac{15-\sqrt{665}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+\sqrt{665}}{2*-1}=\frac{15+\sqrt{665}}{-2}
$