Given the equation
$$\sqrt{\left(3 x^{2} + 4 x\right) - 6} = 2$$
$$\sqrt{3 x^{2} + 4 x - 6} = 2$$
We raise the equation sides to 2-th degree
$$3 x^{2} + 4 x - 6 = 4$$
$$3 x^{2} + 4 x - 6 = 4$$
Transfer the right side of the equation left part with negative sign
$$3 x^{2} + 4 x - 10 = 0$$
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
$$a = 3$$
$$b = 4$$
$$c = -10$$
, then
D = b^2 - 4 * a * c =
(4)^2 - 4 * (3) * (-10) = 136
Because D > 0, then the equation has two roots.
x1 = (-b + sqrt(D)) / (2*a)
x2 = (-b - sqrt(D)) / (2*a)
or
$$x_{1} = - \frac{2}{3} + \frac{\sqrt{34}}{3}$$
$$x_{2} = - \frac{\sqrt{34}}{3} - \frac{2}{3}$$
Because
$$\sqrt{3 x^{2} + 4 x - 6} = 2$$
and
$$\sqrt{3 x^{2} + 4 x - 6} \geq 0$$
then
$$2 \geq 0$$
The final answer:
$$x_{1} = - \frac{2}{3} + \frac{\sqrt{34}}{3}$$
$$x_{2} = - \frac{\sqrt{34}}{3} - \frac{2}{3}$$