Move right part of the equation to
left part with negative sign.
The equation is transformed from
$$\left(8 y + 5\right)^{2} - 128 = - 64 y^{2} + 80 y + 25$$
to
$$\left(\left(8 y + 5\right)^{2} - 128\right) - \left(- 64 y^{2} + 80 y + 25\right) = 0$$
Expand the expression in the equation
$$\left(\left(8 y + 5\right)^{2} - 128\right) - \left(- 64 y^{2} + 80 y + 25\right) = 0$$
We get the quadratic equation
$$128 y^{2} - 128 = 0$$
This equation is of the form
$$a\ y^2 + b\ y + c = 0$$
A quadratic equation can be solved using the discriminant
The roots of the quadratic equation:
$$y_{1} = \frac{\sqrt{D} - b}{2 a}$$
$$y_{2} = \frac{- \sqrt{D} - b}{2 a}$$
where $D = b^2 - 4 a c$ is the discriminant.
Because
$$a = 128$$
$$b = 0$$
$$c = -128$$
, then
$$D = b^2 - 4\ a\ c = $$
$$0^{2} - 128 \cdot 4 \left(-128\right) = 65536$$
Because D > 0, then the equation has two roots.
$$y_1 = \frac{(-b + \sqrt{D})}{2 a}$$
$$y_2 = \frac{(-b - \sqrt{D})}{2 a}$$
or
$$y_{1} = 1$$
Simplify$$y_{2} = -1$$
Simplify