4.81687898=6.28r^2

Solution for 4.81687898=6.28r^2 equation:

4.81687898=6.28r^2

We move all terms to the left:

4.81687898-(6.28r^2)=0

We get rid of parentheses

-6.28r^2+4.81687898=0

a = -6.28; b = 0; c = +4.81687898;
Δ = b2-4ac
Δ = 02-4·(-6.28)·4.81687898
Δ = 120.999999978
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-\sqrt{120.999999978}}{2*-6.28}=\frac{0-\sqrt{120.999999978}}{-12.56}
=-\frac{\sqrt{}}{-12.56}
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{120.999999978}}{2*-6.28}=\frac{0+\sqrt{120.999999978}}{-12.56}
=\frac{\sqrt{}}{-12.56}
$