Move right part of the equation to
left part with negative sign.
The equation is transformed from
$$16 x + 64 = - x^{2}$$
to
$$x^{2} + \left(16 x + 64\right) = 0$$
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 - it is the discriminant.
Because
$$a = 1$$
$$b = 16$$
$$c = 64$$
, then
D = b^2 - 4 * a * c =
(16)^2 - 4 * (1) * (64) = 0
Because D = 0, then the equation has one root.
x = -b/2a = -16/2/(1)
$$x_{1} = -8$$