(20-1x)(200+20x)=0

Solution for (20-1x)(200+20x)=0 equation:

(20-1x)(200+20x)=0

We add all the numbers together, and all the variables

(-1x+20)(20x+200)=0

We multiply parentheses ..

(-20x^2-200x+400x+4000)=0

We get rid of parentheses

-20x^2-200x+400x+4000=0

We add all the numbers together, and all the variables

-20x^2+200x+4000=0

a = -20; b = 200; c = +4000;
Δ = b2-4ac
Δ = 2002-4·(-20)·4000
Δ = 360000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{360000}=600$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(200)-600}{2*-20}=\frac{-800}{-40}
=+20
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(200)+600}{2*-20}=\frac{400}{-40}
=-10
$