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
$$a = -4$$
$$b = -1$$
$$c = 14$$
, then
$$D = b^2 - 4\ a\ c = $$
$$\left(-1\right)^{2} - \left(-4\right) 4 \cdot 14 = 225$$
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$$x_{2} = \frac{7}{4}$$
Simplify