216=(x+6)*x

Solution for 216=(x+6)*x equation:

216=(x+6)*x

We move all terms to the left:

216-((x+6)*x)=0


We calculate terms in parentheses: -((x+6)*x), so:

(x+6)*x

We multiply parentheses

x^2+6x

Back to the equation:

-(x^2+6x)


We get rid of parentheses

-x^2-6x+216=0

We add all the numbers together, and all the variables

-1x^2-6x+216=0

a = -1; b = -6; c = +216;
Δ = b2-4ac
Δ = -62-4·(-1)·216
Δ = 900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{900}=30$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6)-30}{2*-1}=\frac{-24}{-2}
=+12
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6)+30}{2*-1}=\frac{36}{-2}
=-18
$