C(x)=0.1x^2-68x+26,153

Solution for C(x)=0.1x^2-68x+26,153 equation:

(C)=0.1C^2-68C+26.153

We move all terms to the left:

(C)-(0.1C^2-68C+26.153)=0

We get rid of parentheses

-0.1C^2+C+68C-26.153=0

We add all the numbers together, and all the variables

-0.1C^2+69C-26.153=0

a = -0.1; b = 69; c = -26.153;
Δ = b2-4ac
Δ = 692-4·(-0.1)·(-26.153)
Δ = 4750.5388
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{-(69)-\sqrt{4750.5388}}{2*-0.1}=\frac{-69-\sqrt{4750.5388}}{-0.2}
$
$C_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(69)+\sqrt{4750.5388}}{2*-0.1}=\frac{-69+\sqrt{4750.5388}}{-0.2}
$