168-(19-2x)(12-2x)=1380/20

Solution for 168-(19-2x)(12-2x)=1380/20 equation:

168-(19-2x)(12-2x)=1380/20

We move all terms to the left:

168-(19-2x)(12-2x)-(1380/20)=0

We add all the numbers together, and all the variables

-(-2x+19)(-2x+12)+168-69=0

We add all the numbers together, and all the variables

-(-2x+19)(-2x+12)+99=0

We multiply parentheses ..

-(+4x^2-24x-38x+228)+99=0

We get rid of parentheses

-4x^2+24x+38x-228+99=0

We add all the numbers together, and all the variables

-4x^2+62x-129=0

a = -4; b = 62; c = -129;
Δ = b2-4ac
Δ = 622-4·(-4)·(-129)
Δ = 1780
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:

$\sqrt{\Delta}=\sqrt{1780}=\sqrt{4*445}=\sqrt{4}*\sqrt{445}=2\sqrt{445}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(62)-2\sqrt{445}}{2*-4}=\frac{-62-2\sqrt{445}}{-8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(62)+2\sqrt{445}}{2*-4}=\frac{-62+2\sqrt{445}}{-8}
$