(x+6)(x-2)=105

Solution for (x+6)(x-2)=105 equation:

(x+6)(x-2)=105

We move all terms to the left:

(x+6)(x-2)-(105)=0

We multiply parentheses ..

(+x^2-2x+6x-12)-105=0

We get rid of parentheses

x^2-2x+6x-12-105=0

We add all the numbers together, and all the variables

x^2+4x-117=0

a = 1; b = 4; c = -117;
Δ = b2-4ac
Δ = 42-4·1·(-117)
Δ = 484
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{484}=22$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-22}{2*1}=\frac{-26}{2}
=-13
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+22}{2*1}=\frac{18}{2}
=9
$