-2*(x-6)(x+3)=0

Solution for -2*(x-6)(x+3)=0 equation:

-2(x-6)(x+3)=0

We multiply parentheses ..

-2(+x^2+3x-6x-18)=0

We multiply parentheses

-2x^2-6x+12x+36=0

We add all the numbers together, and all the variables

-2x^2+6x+36=0

a = -2; b = 6; c = +36;
Δ = b2-4ac
Δ = 62-4·(-2)·36
Δ = 324
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{324}=18$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-18}{2*-2}=\frac{-24}{-4}
=+6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+18}{2*-2}=\frac{12}{-4}
=-3
$