(100-x)*(100+2x)=0

Solution for (100-x)*(100+2x)=0 equation:

(100-x)(100+2x)=0

We add all the numbers together, and all the variables

(-1x+100)(2x+100)=0

We multiply parentheses ..

(-2x^2-100x+200x+10000)=0

We get rid of parentheses

-2x^2-100x+200x+10000=0

We add all the numbers together, and all the variables

-2x^2+100x+10000=0

a = -2; b = 100; c = +10000;
Δ = b2-4ac
Δ = 1002-4·(-2)·10000
Δ = 90000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{90000}=300$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(100)-300}{2*-2}=\frac{-400}{-4}
=+100
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(100)+300}{2*-2}=\frac{200}{-4}
=-50
$