5=2(3.14)r2

Solution for 5=2(3.14)r2 equation:

5=2(3.14)r2

We move all terms to the left:

5-(2(3.14)r2)=0


We calculate terms in parentheses: -(2(3.14)r2), so:

2(3.14)r2

We multiply parentheses

6.28r^2

Back to the equation:

-(6.28r^2)


We get rid of parentheses

-6.28r^2+5=0

a = -6.28; b = 0; c = +5;
Δ = b2-4ac
Δ = 02-4·(-6.28)·5
Δ = 125.6
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{125.6}}{2*-6.28}=\frac{0-\sqrt{125.6}}{-12.56}
=-\frac{\sqrt{}}{-12.56}
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{125.6}}{2*-6.28}=\frac{0+\sqrt{125.6}}{-12.56}
=\frac{\sqrt{}}{-12.56}
$