(x+2)(x-8)=0 equation

Expand the expression in the equation
$$\left(x + 2\right) \left(x - 8\right) + 0 = 0$$
We get the quadratic equation
$$x^{2} - 6 x - 16 = 0$$
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
$$a = 1$$
$$b = -6$$
$$c = -16$$
, then
$$D = b^2 - 4 * a * c = $$
$$\left(-6\right)^{2} - 1 \cdot 4 \left(-16\right) = 100$$
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
$$x_{1} = 8$$
Simplify
$$x_{2} = -2$$
Simplify