13,000=-15x^2+300x=12,000

Solution for 13,000=-15x^2+300x=12,000 equation:

13.000=-15x^2+300x=12.000

We move all terms to the left:

13.000-(-15x^2+300x)=0

We add all the numbers together, and all the variables

-(-15x^2+300x)+13=0

We get rid of parentheses

15x^2-300x+13=0

a = 15; b = -300; c = +13;
Δ = b2-4ac
Δ = -3002-4·15·13
Δ = 89220
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{89220}=\sqrt{4*22305}=\sqrt{4}*\sqrt{22305}=2\sqrt{22305}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-300)-2\sqrt{22305}}{2*15}=\frac{300-2\sqrt{22305}}{30}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-300)+2\sqrt{22305}}{2*15}=\frac{300+2\sqrt{22305}}{30}
$