Given the equation:
$$\frac{\left(y^{4} + 4 y^{2}\right) - 12}{4} = 0$$
Do replacement
$$v = y^{2}$$
then the equation will be the:
$$\frac{v^{2}}{4} + v - 3 = 0$$
This equation is of the form
a*v^2 + b*v + c = 0
A quadratic equation can be solved
using the discriminant.
The roots of the quadratic equation:
$$v_{1} = \frac{\sqrt{D} - b}{2 a}$$
$$v_{2} = \frac{- \sqrt{D} - b}{2 a}$$
where D = b^2 - 4*a*c - it is the discriminant.
Because
$$a = \frac{1}{4}$$
$$b = 1$$
$$c = -3$$
, then
D = b^2 - 4 * a * c =
(1)^2 - 4 * (1/4) * (-3) = 4
Because D > 0, then the equation has two roots.
v1 = (-b + sqrt(D)) / (2*a)
v2 = (-b - sqrt(D)) / (2*a)
or
$$v_{1} = 2$$
$$v_{2} = -6$$
The final answer:
Because
$$v = y^{2}$$
then
$$y_{1} = \sqrt{v_{1}}$$
$$y_{2} = - \sqrt{v_{1}}$$
$$y_{3} = \sqrt{v_{2}}$$
$$y_{4} = - \sqrt{v_{2}}$$
then:
$$y_{1} = $$
$$\frac{0}{1} + \frac{2^{\frac{1}{2}}}{1} = \sqrt{2}$$
$$y_{2} = $$
$$\frac{\left(-1\right) 2^{\frac{1}{2}}}{1} + \frac{0}{1} = - \sqrt{2}$$
$$y_{3} = $$
$$\frac{0}{1} + \frac{\left(-6\right)^{\frac{1}{2}}}{1} = \sqrt{6} i$$
$$y_{4} = $$
$$\frac{0}{1} + \frac{\left(-1\right) \left(-6\right)^{\frac{1}{2}}}{1} = - \sqrt{6} i$$