C(x)=2x^2-720x+85,000

Solution for C(x)=2x^2-720x+85,000 equation:

(C)=2C^2-720C+85.000

We move all terms to the left:

(C)-(2C^2-720C+85.000)=0

We get rid of parentheses

-2C^2+C+720C-85.000=0

We add all the numbers together, and all the variables

-2C^2+721C-85=0

a = -2; b = 721; c = -85;
Δ = b2-4ac
Δ = 7212-4·(-2)·(-85)
Δ = 519161
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$C_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$C_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$C_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(721)-\sqrt{519161}}{2*-2}=\frac{-721-\sqrt{519161}}{-4}
$
$C_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(721)+\sqrt{519161}}{2*-2}=\frac{-721+\sqrt{519161}}{-4}
$