(2x+40)*(2x+20)=800

Solution for (2x+40)*(2x+20)=800 equation:

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

We move all terms to the left:

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

We multiply parentheses ..

(+4x^2+40x+80x+800)-800=0

We get rid of parentheses

4x^2+40x+80x+800-800=0

We add all the numbers together, and all the variables

4x^2+120x=0

a = 4; b = 120; c = 0;
Δ = b2-4ac
Δ = 1202-4·4·0
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{-(120)-120}{2*4}=\frac{-240}{8}
=-30
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(120)+120}{2*4}=\frac{0}{8}
=0
$