x^4-3x^2-20=0

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Solution for x^4-3x^2-20=0 equation:


Simplifying
x4 + -3x2 + -20 = 0

Reorder the terms:
-20 + -3x2 + x4 = 0

Solving
-20 + -3x2 + x4 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '20' to each side of the equation.
-20 + -3x2 + 20 + x4 = 0 + 20

Reorder the terms:
-20 + 20 + -3x2 + x4 = 0 + 20

Combine like terms: -20 + 20 = 0
0 + -3x2 + x4 = 0 + 20
-3x2 + x4 = 0 + 20

Combine like terms: 0 + 20 = 20
-3x2 + x4 = 20

The x term is -3x2.  Take half its coefficient (-1.5).
Square it (2.25) and add it to both sides.

Add '2.25' to each side of the equation.
-3x2 + 2.25 + x4 = 20 + 2.25

Reorder the terms:
2.25 + -3x2 + x4 = 20 + 2.25

Combine like terms: 20 + 2.25 = 22.25
2.25 + -3x2 + x4 = 22.25

Factor a perfect square on the left side:
(x2 + -1.5)(x2 + -1.5) = 22.25

Calculate the square root of the right side: 4.716990566

Break this problem into two subproblems by setting 
(x2 + -1.5) equal to 4.716990566 and -4.716990566.

Subproblem 1

x2 + -1.5 = 4.716990566 Simplifying x2 + -1.5 = 4.716990566 Reorder the terms: -1.5 + x2 = 4.716990566 Solving -1.5 + x2 = 4.716990566 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.5' to each side of the equation. -1.5 + 1.5 + x2 = 4.716990566 + 1.5 Combine like terms: -1.5 + 1.5 = 0.0 0.0 + x2 = 4.716990566 + 1.5 x2 = 4.716990566 + 1.5 Combine like terms: 4.716990566 + 1.5 = 6.216990566 x2 = 6.216990566 Simplifying x2 = 6.216990566 Take the square root of each side: x = {-2.493389373, 2.493389373}

Subproblem 2

x2 + -1.5 = -4.716990566 Simplifying x2 + -1.5 = -4.716990566 Reorder the terms: -1.5 + x2 = -4.716990566 Solving -1.5 + x2 = -4.716990566 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '1.5' to each side of the equation. -1.5 + 1.5 + x2 = -4.716990566 + 1.5 Combine like terms: -1.5 + 1.5 = 0.0 0.0 + x2 = -4.716990566 + 1.5 x2 = -4.716990566 + 1.5 Combine like terms: -4.716990566 + 1.5 = -3.216990566 x2 = -3.216990566 Simplifying x2 = -3.216990566 Reorder the terms: 3.216990566 + x2 = -3.216990566 + 3.216990566 Combine like terms: -3.216990566 + 3.216990566 = 0.000000000 3.216990566 + x2 = 0.000000000 The solution to this equation could not be determined.This subproblem is being ignored because a solution could not be determined. The solution to this equation could not be determined.

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