(3x-18)(5x+10)=0

Solution for (3x-18)(5x+10)=0 equation:

(3x-18)(5x+10)=0

We multiply parentheses ..

(+15x^2+30x-90x-180)=0

We get rid of parentheses

15x^2+30x-90x-180=0

We add all the numbers together, and all the variables

15x^2-60x-180=0

a = 15; b = -60; c = -180;
Δ = b2-4ac
Δ = -602-4·15·(-180)
Δ = 14400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{14400}=120$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-60)-120}{2*15}=\frac{-60}{30}
=-2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-60)+120}{2*15}=\frac{180}{30}
=6
$