x2-20x=4

Solution for x2-20x=4 equation:

x2-20x=4

We move all terms to the left:

x2-20x-(4)=0

We add all the numbers together, and all the variables

x^2-20x-4=0

a = 1; b = -20; c = -4;
Δ = b2-4ac
Δ = -202-4·1·(-4)
Δ = 416
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:

$\sqrt{\Delta}=\sqrt{416}=\sqrt{16*26}=\sqrt{16}*\sqrt{26}=4\sqrt{26}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-4\sqrt{26}}{2*1}=\frac{20-4\sqrt{26}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+4\sqrt{26}}{2*1}=\frac{20+4\sqrt{26}}{2}
$