8r=3.14r^2

Solution for 8r=3.14r^2 equation:

8r=3.14r^2

We move all terms to the left:

8r-(3.14r^2)=0

We get rid of parentheses

-3.14r^2+8r=0

a = -3.14; b = 8; c = 0;
Δ = b2-4ac
Δ = 82-4·(-3.14)·0
Δ = 64
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{64}=8$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-8}{2*-3.14}=\frac{-16}{-6.28}
=2+1/1.8255813953488
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+8}{2*-3.14}=\frac{0}{-6.28}
=0
$