Expand the expression in the equation
$$- \left(4 x + 3\right)^{2} + \left(7 x - 2\right)^{2} = 0$$
We get the quadratic equation
$$33 x^{2} - 52 x - 5 = 0$$
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
$$a = 33$$
$$b = -52$$
$$c = -5$$
, then
D = b^2 - 4 * a * c =
(-52)^2 - 4 * (33) * (-5) = 3364
Because D > 0, then the equation has two roots.
x1 = (-b + sqrt(D)) / (2*a)
x2 = (-b - sqrt(D)) / (2*a)
or
$$x_{1} = \frac{5}{3}$$
$$x_{2} = - \frac{1}{11}$$