3(4x-5)(x+10)=0

Solution for 3(4x-5)(x+10)=0 equation:

3(4x-5)(x+10)=0

We multiply parentheses ..

3(+4x^2+40x-5x-50)=0

We multiply parentheses

12x^2+120x-15x-150=0

We add all the numbers together, and all the variables

12x^2+105x-150=0

a = 12; b = 105; c = -150;
Δ = b2-4ac
Δ = 1052-4·12·(-150)
Δ = 18225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{18225}=135$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(105)-135}{2*12}=\frac{-240}{24}
=-10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(105)+135}{2*12}=\frac{30}{24}
=1+1/4
$