(20-2x)(25-2x)=130

Solution for (20-2x)(25-2x)=130 equation:

(20-2x)(25-2x)=130

We move all terms to the left:

(20-2x)(25-2x)-(130)=0

We add all the numbers together, and all the variables

(-2x+20)(-2x+25)-130=0

We multiply parentheses ..

(+4x^2-50x-40x+500)-130=0

We get rid of parentheses

4x^2-50x-40x+500-130=0

We add all the numbers together, and all the variables

4x^2-90x+370=0

a = 4; b = -90; c = +370;
Δ = b2-4ac
Δ = -902-4·4·370
Δ = 2180
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{2180}=\sqrt{4*545}=\sqrt{4}*\sqrt{545}=2\sqrt{545}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-90)-2\sqrt{545}}{2*4}=\frac{90-2\sqrt{545}}{8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-90)+2\sqrt{545}}{2*4}=\frac{90+2\sqrt{545}}{8}
$