9964=9439.9+24.26024311*x+-0.07508511*x^2

Solution for 9964=9439.9+24.26024311*x+-0.07508511*x^2 equation:

9964=9439.9+24.26024311x+-0.07508511x^2

We move all terms to the left:

9964-(9439.9+24.26024311x+-0.07508511x^2)=0

We use the square of the difference formula

-(9439.9+24.26024311x-0.07508511x^2)+9964=0

We get rid of parentheses

0.07508511x^2-24.26024311x-9439.9+9964=0

We add all the numbers together, and all the variables

0.07508511x^2-24.26024311x+524.1=0

a = 0.07508511; b = -24.26024311; c = +524.1;
Δ = b2-4ac
Δ = -24.260243112-4·0.07508511·524.1
Δ = 431.150971152
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-24.26024311)-\sqrt{431.150971152}}{2*0.07508511}=\frac{24.26024311-\sqrt{431.150971152}}{0.15017022}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-24.26024311)+\sqrt{431.150971152}}{2*0.07508511}=\frac{24.26024311+\sqrt{431.150971152}}{0.15017022}
$