0=12x+x^2-864

Solution for 0=12x+x^2-864 equation:

0=12x+x^2-864

We move all terms to the left:

0-(12x+x^2-864)=0

We add all the numbers together, and all the variables

-(12x+x^2-864)=0

We get rid of parentheses

-x^2-12x+864=0

We add all the numbers together, and all the variables

-1x^2-12x+864=0

a = -1; b = -12; c = +864;
Δ = b2-4ac
Δ = -122-4·(-1)·864
Δ = 3600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3600}=60$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-60}{2*-1}=\frac{-48}{-2}
=+24
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+60}{2*-1}=\frac{72}{-2}
=-36
$