(12+x)*x=540

Solution for (12+x)*x=540 equation:

(12+x)*x=540

We move all terms to the left:

(12+x)*x-(540)=0

We add all the numbers together, and all the variables

(x+12)*x-540=0

We multiply parentheses

x^2+12x-540=0

a = 1; b = 12; c = -540;
Δ = b2-4ac
Δ = 122-4·1·(-540)
Δ = 2304
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2304}=48$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-48}{2*1}=\frac{-60}{2}
=-30
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+48}{2*1}=\frac{36}{2}
=18
$