x^4-400=0

Solution for x^4-400=0 equation:

Simplifying
x4 + -400 = 0

Reorder the terms:
-400 + x4 = 0

Solving
-400 + x4 = 0

Solving for variable 'x'.

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

Add '400' to each side of the equation.
-400 + 400 + x4 = 0 + 400

Combine like terms: -400 + 400 = 0
0 + x4 = 0 + 400
x4 = 0 + 400

Combine like terms: 0 + 400 = 400
x4 = 400

Simplifying
x4 = 400

Reorder the terms:
-400 + x4 = 400 + -400

Combine like terms: 400 + -400 = 0
-400 + x4 = 0

Factor a difference between two squares.
(20 + x2)(-20 + x2) = 0

Subproblem 1
Set the factor '(20 + x2)' equal to zero and attempt to solve:

Simplifying
20 + x2 = 0

Solving
20 + x2 = 0

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

Add '-20' to each side of the equation.
20 + -20 + x2 = 0 + -20

Combine like terms: 20 + -20 = 0
0 + x2 = 0 + -20
x2 = 0 + -20

Combine like terms: 0 + -20 = -20
x2 = -20

Simplifying
x2 = -20

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 '(-20 + x2)' equal to zero and attempt to solve:

Simplifying
-20 + x2 = 0

Solving
-20 + x2 = 0

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

Add '20' to each side of the equation.
-20 + 20 + x2 = 0 + 20

Combine like terms: -20 + 20 = 0
0 + x2 = 0 + 20
x2 = 0 + 20

Combine like terms: 0 + 20 = 20
x2 = 20

Simplifying
x2 = 20

Take the square root of each side:
x = {-4.472135955, 4.472135955}
Solution
x = {-4.472135955, 4.472135955}