(-5x-15)(-10-5x)=0

Solution for (-5x-15)(-10-5x)=0 equation:

(-5x-15)(-10-5x)=0

We add all the numbers together, and all the variables

(-5x-15)(-5x-10)=0

We multiply parentheses ..

(+25x^2+50x+75x+150)=0

We get rid of parentheses

25x^2+50x+75x+150=0

We add all the numbers together, and all the variables

25x^2+125x+150=0

a = 25; b = 125; c = +150;
Δ = b2-4ac
Δ = 1252-4·25·150
Δ = 625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{625}=25$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(125)-25}{2*25}=\frac{-150}{50}
=-3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(125)+25}{2*25}=\frac{-100}{50}
=-2
$