R(x)=-20x^2+1400x+36000

Solution for R(x)=-20x^2+1400x+36000 equation:

(R)=-20R^2+1400R+36000

We move all terms to the left:

(R)-(-20R^2+1400R+36000)=0

We get rid of parentheses

20R^2-1400R+R-36000=0

We add all the numbers together, and all the variables

20R^2-1399R-36000=0

a = 20; b = -1399; c = -36000;
Δ = b2-4ac
Δ = -13992-4·20·(-36000)
Δ = 4837201
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{-(-1399)-\sqrt{4837201}}{2*20}=\frac{1399-\sqrt{4837201}}{40}
$
$R_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1399)+\sqrt{4837201}}{2*20}=\frac{1399+\sqrt{4837201}}{40}
$