-(10x-4)(x+3)=0

Solution for -(10x-4)(x+3)=0 equation:

-(10x-4)(x+3)=0

We multiply parentheses ..

-(+10x^2+30x-4x-12)=0

We get rid of parentheses

-10x^2-30x+4x+12=0

We add all the numbers together, and all the variables

-10x^2-26x+12=0

a = -10; b = -26; c = +12;
Δ = b2-4ac
Δ = -262-4·(-10)·12
Δ = 1156
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1156}=34$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-26)-34}{2*-10}=\frac{-8}{-20}
=2/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-26)+34}{2*-10}=\frac{60}{-20}
=-3
$