6(x+4)(x-5)=0

Solution for 6(x+4)(x-5)=0 equation:

6(x+4)(x-5)=0

We multiply parentheses ..

6(+x^2-5x+4x-20)=0

We multiply parentheses

6x^2-30x+24x-120=0

We add all the numbers together, and all the variables

6x^2-6x-120=0

a = 6; b = -6; c = -120;
Δ = b2-4ac
Δ = -62-4·6·(-120)
Δ = 2916
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2916}=54$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6)-54}{2*6}=\frac{-48}{12}
=-4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6)+54}{2*6}=\frac{60}{12}
=5
$