36=(x+9)x

Solution for 36=(x+9)x equation:

36=(x+9)x

We move all terms to the left:

36-((x+9)x)=0


We calculate terms in parentheses: -((x+9)x), so:

(x+9)x

We multiply parentheses

x^2+9x

Back to the equation:

-(x^2+9x)


We get rid of parentheses

-x^2-9x+36=0

We add all the numbers together, and all the variables

-1x^2-9x+36=0

a = -1; b = -9; c = +36;
Δ = b2-4ac
Δ = -92-4·(-1)·36
Δ = 225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{225}=15$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-15}{2*-1}=\frac{-6}{-2}
=+3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+15}{2*-1}=\frac{24}{-2}
=-12
$