4c^2=20

Solution for 4c^2=20 equation:

4c^2=20

We move all terms to the left:

4c^2-(20)=0

a = 4; b = 0; c = -20;
Δ = b2-4ac
Δ = 02-4·4·(-20)
Δ = 320
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{320}=\sqrt{64*5}=\sqrt{64}*\sqrt{5}=8\sqrt{5}$
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-8\sqrt{5}}{2*4}=\frac{0-8\sqrt{5}}{8}
=-\frac{8\sqrt{5}}{8}
=-\sqrt{5}
$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+8\sqrt{5}}{2*4}=\frac{0+8\sqrt{5}}{8}
=\frac{8\sqrt{5}}{8}
=\sqrt{5}
$