x^4+9x^2-18=0

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Solution for x^4+9x^2-18=0 equation:


Simplifying
x4 + 9x2 + -18 = 0

Reorder the terms:
-18 + 9x2 + x4 = 0

Solving
-18 + 9x2 + x4 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '18' to each side of the equation.
-18 + 9x2 + 18 + x4 = 0 + 18

Reorder the terms:
-18 + 18 + 9x2 + x4 = 0 + 18

Combine like terms: -18 + 18 = 0
0 + 9x2 + x4 = 0 + 18
9x2 + x4 = 0 + 18

Combine like terms: 0 + 18 = 18
9x2 + x4 = 18

The x term is 9x2.  Take half its coefficient (4.5).
Square it (20.25) and add it to both sides.

Add '20.25' to each side of the equation.
9x2 + 20.25 + x4 = 18 + 20.25

Reorder the terms:
20.25 + 9x2 + x4 = 18 + 20.25

Combine like terms: 18 + 20.25 = 38.25
20.25 + 9x2 + x4 = 38.25

Factor a perfect square on the left side:
(x2 + 4.5)(x2 + 4.5) = 38.25

Calculate the square root of the right side: 6.184658438

Break this problem into two subproblems by setting 
(x2 + 4.5) equal to 6.184658438 and -6.184658438.

Subproblem 1

x2 + 4.5 = 6.184658438 Simplifying x2 + 4.5 = 6.184658438 Reorder the terms: 4.5 + x2 = 6.184658438 Solving 4.5 + x2 = 6.184658438 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + x2 = 6.184658438 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x2 = 6.184658438 + -4.5 x2 = 6.184658438 + -4.5 Combine like terms: 6.184658438 + -4.5 = 1.684658438 x2 = 1.684658438 Simplifying x2 = 1.684658438 Take the square root of each side: x = {-1.297943927, 1.297943927}

Subproblem 2

x2 + 4.5 = -6.184658438 Simplifying x2 + 4.5 = -6.184658438 Reorder the terms: 4.5 + x2 = -6.184658438 Solving 4.5 + x2 = -6.184658438 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-4.5' to each side of the equation. 4.5 + -4.5 + x2 = -6.184658438 + -4.5 Combine like terms: 4.5 + -4.5 = 0.0 0.0 + x2 = -6.184658438 + -4.5 x2 = -6.184658438 + -4.5 Combine like terms: -6.184658438 + -4.5 = -10.684658438 x2 = -10.684658438 Simplifying x2 = -10.684658438 Reorder the terms: 10.684658438 + x2 = -10.684658438 + 10.684658438 Combine like terms: -10.684658438 + 10.684658438 = 0.000000000 10.684658438 + 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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