R(x)=-0.4x2+360x

Solution for R(x)=-0.4x2+360x equation:

(R)=-0.4R^2+360R

We move all terms to the left:

(R)-(-0.4R^2+360R)=0

We get rid of parentheses

0.4R^2-360R+R=0

We add all the numbers together, and all the variables

0.4R^2-359R=0

a = 0.4; b = -359; c = 0;
Δ = b2-4ac
Δ = -3592-4·0.4·0
Δ = 128881
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$R_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$R_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{128881}=359$
$R_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-359)-359}{2*0.4}=\frac{0}{0.8}
=0
$
$R_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-359)+359}{2*0.4}=\frac{718}{0.8}
=897+0.4/0.8
$