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