(2x+20)(2x+40)=1664

Solution for (2x+20)(2x+40)=1664 equation:

(2x+20)(2x+40)=1664

We move all terms to the left:

(2x+20)(2x+40)-(1664)=0

We multiply parentheses ..

(+4x^2+80x+40x+800)-1664=0

We get rid of parentheses

4x^2+80x+40x+800-1664=0

We add all the numbers together, and all the variables

4x^2+120x-864=0

a = 4; b = 120; c = -864;
Δ = b2-4ac
Δ = 1202-4·4·(-864)
Δ = 28224
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{28224}=168$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(120)-168}{2*4}=\frac{-288}{8}
=-36
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(120)+168}{2*4}=\frac{48}{8}
=6
$