x(2x+6)=36

Solution for x(2x+6)=36 equation:

x(2x+6)=36

We move all terms to the left:

x(2x+6)-(36)=0

We multiply parentheses

2x^2+6x-36=0

a = 2; b = 6; c = -36;
Δ = b2-4ac
Δ = 62-4·2·(-36)
Δ = 324
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{324}=18$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-18}{2*2}=\frac{-24}{4}
=-6
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+18}{2*2}=\frac{12}{4}
=3
$