28x^4-5x^2-3=0

Solution for 28x^4-5x^2-3=0 equation:

Simplifying
28x4 + -5x2 + -3 = 0

Reorder the terms:
-3 + -5x2 + 28x4 = 0

Solving
-3 + -5x2 + 28x4 = 0

Solving for variable 'x'.

Factor a trinomial.
(-1 + -4x2)(3 + -7x2) = 0

Subproblem 1
Set the factor '(-1 + -4x2)' equal to zero and attempt to solve:

Simplifying
-1 + -4x2 = 0

Solving
-1 + -4x2 = 0

Move all terms containing x to the left, all other terms to the right.

Add '1' to each side of the equation.
-1 + 1 + -4x2 = 0 + 1

Combine like terms: -1 + 1 = 0
0 + -4x2 = 0 + 1
-4x2 = 0 + 1

Combine like terms: 0 + 1 = 1
-4x2 = 1

Divide each side by '-4'.
x2 = -0.25

Simplifying
x2 = -0.25

The solution to this equation could not be determined.

This subproblem is being ignored because a solution could not be determined.
Subproblem 2
Set the factor '(3 + -7x2)' equal to zero and attempt to solve:

Simplifying
3 + -7x2 = 0

Solving
3 + -7x2 = 0

Move all terms containing x to the left, all other terms to the right.

Add '-3' to each side of the equation.
3 + -3 + -7x2 = 0 + -3

Combine like terms: 3 + -3 = 0
0 + -7x2 = 0 + -3
-7x2 = 0 + -3

Combine like terms: 0 + -3 = -3
-7x2 = -3

Divide each side by '-7'.
x2 = 0.4285714286

Simplifying
x2 = 0.4285714286

Take the square root of each side:
x = {-0.654653671, 0.654653671}
Solution
x = {-0.654653671, 0.654653671}