(x+20)(x+40)=0

Solution for (x+20)(x+40)=0 equation:

(x+20)(x+40)=0

We multiply parentheses ..

(+x^2+40x+20x+800)=0

We get rid of parentheses

x^2+40x+20x+800=0

We add all the numbers together, and all the variables

x^2+60x+800=0

a = 1; b = 60; c = +800;
Δ = b2-4ac
Δ = 602-4·1·800
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(60)-20}{2*1}=\frac{-80}{2}
=-40
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(60)+20}{2*1}=\frac{-40}{2}
=-20
$