(x^4)+(15x^2)-16=0

Solution for (x^4)+(15x^2)-16=0 equation:

Simplifying
(x4) + (15x2) + -16 = 0
x4 + (15x2) + -16 = 0

Reorder the terms:
-16 + (15x2) + x4 = 0

Solving
-16 + (15x2) + x4 = 0

Solving for variable 'x'.

Factor a trinomial.
(-16 + -1x2)(1 + -1x2) = 0

Factor a difference between two squares.
(-16 + -1x2)((1 + x)(1 + -1x)) = 0

Subproblem 1
Set the factor '(-16 + -1x2)' equal to zero and attempt to solve:

Simplifying
-16 + -1x2 = 0

Solving
-16 + -1x2 = 0

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

Add '16' to each side of the equation.
-16 + 16 + -1x2 = 0 + 16

Combine like terms: -16 + 16 = 0
0 + -1x2 = 0 + 16
-1x2 = 0 + 16

Combine like terms: 0 + 16 = 16
-1x2 = 16

Divide each side by '-1'.
x2 = -16

Simplifying
x2 = -16

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 '(1 + x)' equal to zero and attempt to solve:

Simplifying
1 + x = 0

Solving
1 + x = 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 + x = 0 + -1

Combine like terms: 1 + -1 = 0
0 + x = 0 + -1
x = 0 + -1

Combine like terms: 0 + -1 = -1
x = -1

Simplifying
x = -1
Subproblem 3
Set the factor '(1 + -1x)' equal to zero and attempt to solve:

Simplifying
1 + -1x = 0

Solving
1 + -1x = 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 + -1x = 0 + -1

Combine like terms: 1 + -1 = 0
0 + -1x = 0 + -1
-1x = 0 + -1

Combine like terms: 0 + -1 = -1
-1x = -1

Divide each side by '-1'.
x = 1

Simplifying
x = 1
Solution
x = {-1, 1}