(20-2x)(40-2x)=476

Solution for (20-2x)(40-2x)=476 equation:

(20-2x)(40-2x)=476

We move all terms to the left:

(20-2x)(40-2x)-(476)=0

We add all the numbers together, and all the variables

(-2x+20)(-2x+40)-476=0

We multiply parentheses ..

(+4x^2-80x-40x+800)-476=0

We get rid of parentheses

4x^2-80x-40x+800-476=0

We add all the numbers together, and all the variables

4x^2-120x+324=0

a = 4; b = -120; c = +324;
Δ = b2-4ac
Δ = -1202-4·4·324
Δ = 9216
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{9216}=96$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-120)-96}{2*4}=\frac{24}{8}
=3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-120)+96}{2*4}=\frac{216}{8}
=27
$