(x)=-1500+12x-0.004x^2

Solution for (x)=-1500+12x-0.004x^2 equation:

(x)=-1500+12x-0.004x^2

We move all terms to the left:

(x)-(-1500+12x-0.004x^2)=0

We get rid of parentheses

0.004x^2-12x+x+1500=0

We add all the numbers together, and all the variables

0.004x^2-11x+1500=0

a = 0.004; b = -11; c = +1500;
Δ = b2-4ac
Δ = -112-4·0.004·1500
Δ = 97
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{-(-11)-\sqrt{97}}{2*0.004}=\frac{11-\sqrt{97}}{0.008}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-11)+\sqrt{97}}{2*0.004}=\frac{11+\sqrt{97}}{0.008}
$