0=x^4-2x^2-15

Solution for 0=x^4-2x^2-15 equation:

Simplifying
0 = x4 + -2x2 + -15

Reorder the terms:
0 = -15 + -2x2 + x4

Solving
0 = -15 + -2x2 + x4

Solving for variable 'x'.

Combine like terms: 0 + 15 = 15
15 + 2x2 + -1x4 = -15 + -2x2 + x4 + 15 + 2x2 + -1x4

Reorder the terms:
15 + 2x2 + -1x4 = -15 + 15 + -2x2 + 2x2 + x4 + -1x4

Combine like terms: -15 + 15 = 0
15 + 2x2 + -1x4 = 0 + -2x2 + 2x2 + x4 + -1x4
15 + 2x2 + -1x4 = -2x2 + 2x2 + x4 + -1x4

Combine like terms: -2x2 + 2x2 = 0
15 + 2x2 + -1x4 = 0 + x4 + -1x4
15 + 2x2 + -1x4 = x4 + -1x4

Combine like terms: x4 + -1x4 = 0
15 + 2x2 + -1x4 = 0

Factor a trinomial.
(5 + -1x2)(3 + x2) = 0

Subproblem 1
Set the factor '(5 + -1x2)' equal to zero and attempt to solve:

Simplifying
5 + -1x2 = 0

Solving
5 + -1x2 = 0

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

Add '-5' to each side of the equation.
5 + -5 + -1x2 = 0 + -5

Combine like terms: 5 + -5 = 0
0 + -1x2 = 0 + -5
-1x2 = 0 + -5

Combine like terms: 0 + -5 = -5
-1x2 = -5

Divide each side by '-1'.
x2 = 5

Simplifying
x2 = 5

Take the square root of each side:
x = {-2.236067978, 2.236067978}
Subproblem 2
Set the factor '(3 + x2)' equal to zero and attempt to solve:

Simplifying
3 + x2 = 0

Solving
3 + x2 = 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 + x2 = 0 + -3

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

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

Simplifying
x2 = -3

The solution to this equation could not be determined.

This subproblem is being ignored because a solution could not be determined.
Solution
x = {-2.236067978, 2.236067978}