r(4.6)r=81

Solution for r(4.6)r=81 equation:

r(4.6)r=81

We move all terms to the left:

r(4.6)r-(81)=0

We multiply parentheses

4.6r^2-81=0

a = 4.6; b = 0; c = -81;
Δ = b2-4ac
Δ = 02-4·4.6·(-81)
Δ = 1490.4
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{1490.4}}{2*4.6}=\frac{0-\sqrt{1490.4}}{9.2}
=-\frac{\sqrt{}}{9.2}
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{1490.4}}{2*4.6}=\frac{0+\sqrt{1490.4}}{9.2}
=\frac{\sqrt{}}{9.2}
$