8x^4-54x^2+81=0

Solution for 8x^4-54x^2+81=0 equation:

Simplifying
8x4 + -54x2 + 81 = 0

Reorder the terms:
81 + -54x2 + 8x4 = 0

Solving
81 + -54x2 + 8x4 = 0

Solving for variable 'x'.

Factor a trinomial.
(9 + -4x2)(9 + -2x2) = 0

Factor a difference between two squares.
((3 + 2x)(3 + -2x))(9 + -2x2) = 0

Subproblem 1
Set the factor '(9 + -2x2)' equal to zero and attempt to solve:

Simplifying
9 + -2x2 = 0

Solving
9 + -2x2 = 0

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

Add '-9' to each side of the equation.
9 + -9 + -2x2 = 0 + -9

Combine like terms: 9 + -9 = 0
0 + -2x2 = 0 + -9
-2x2 = 0 + -9

Combine like terms: 0 + -9 = -9
-2x2 = -9

Divide each side by '-2'.
x2 = 4.5

Simplifying
x2 = 4.5

Take the square root of each side:
x = {-2.121320344, 2.121320344}
Subproblem 2
Set the factor '(3 + 2x)' equal to zero and attempt to solve:

Simplifying
3 + 2x = 0

Solving
3 + 2x = 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 + 2x = 0 + -3

Combine like terms: 3 + -3 = 0
0 + 2x = 0 + -3
2x = 0 + -3

Combine like terms: 0 + -3 = -3
2x = -3

Divide each side by '2'.
x = -1.5

Simplifying
x = -1.5
Subproblem 3
Set the factor '(3 + -2x)' equal to zero and attempt to solve:

Simplifying
3 + -2x = 0

Solving
3 + -2x = 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 + -2x = 0 + -3

Combine like terms: 3 + -3 = 0
0 + -2x = 0 + -3
-2x = 0 + -3

Combine like terms: 0 + -3 = -3
-2x = -3

Divide each side by '-2'.
x = 1.5

Simplifying
x = 1.5
Solution
x = {-2.121320344, 2.121320344, -1.5, 1.5}