R=56x-0.01x2

Solution for R=56x-0.01x2 equation:

=56R-0.01R^2

We move all terms to the left:

-(56R-0.01R^2)=0

We get rid of parentheses

0.01R^2-56R=0

a = 0.01; b = -56; c = 0;
Δ = b2-4ac
Δ = -562-4·0.01·0
Δ = 3136
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$R_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$R_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3136}=56$
$R_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-56)-56}{2*0.01}=\frac{0}{0.02}
=0
$
$R_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-56)+56}{2*0.01}=\frac{112}{0.02}
=5600
$