20736=4x^2

Solution for 20736=4x^2 equation:

20736=4x^2

We move all terms to the left:

20736-(4x^2)=0

a = -4; b = 0; c = +20736;
Δ = b2-4ac
Δ = 02-4·(-4)·20736
Δ = 331776
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{331776}=576$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-576}{2*-4}=\frac{-576}{-8}
=+72
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+576}{2*-4}=\frac{576}{-8}
=-72
$