Move right part of the equation to
left part with negative sign.
The equation is transformed from
$$12 x = 3 x^{2} - 36$$
to
$$12 x - \left(3 x^{2} - 36\right) = 0$$
This equation is of the form
$$a*x^2 + b*x + c = 0$$
A quadratic equation can be solved using the discriminant
The roots of the quadratic equation:
$$x_{1} = \frac{\sqrt{D} - b}{2 a}$$
$$x_{2} = \frac{- \sqrt{D} - b}{2 a}$$
where $D = b^2 - 4 a c$ is the discriminant.
Because
$$a = -3$$
$$b = 12$$
$$c = 36$$
, then
$$D = b^2 - 4 * a * c = $$
$$12^{2} - \left(-3\right) 4 \cdot 36 = 576$$
Because D > 0, then the equation has two roots.
$$x_1 = \frac{(-b + \sqrt{D})}{2 a}$$
$$x_2 = \frac{(-b - \sqrt{D})}{2 a}$$
or
$$x_{1} = -2$$
Simplify$$x_{2} = 6$$
Simplify