15x^4+84x^2-36=0

Solution for 15x^4+84x^2-36=0 equation:

Simplifying
15x4 + 84x2 + -36 = 0

Reorder the terms:
-36 + 84x2 + 15x4 = 0

Solving
-36 + 84x2 + 15x4 = 0

Solving for variable 'x'.

Factor out the Greatest Common Factor (GCF), '3'.
3(-12 + 28x2 + 5x4) = 0

Factor a trinomial.
3((-6 + -1x2)(2 + -5x2)) = 0

Ignore the factor 3.
Subproblem 1
Set the factor '(-6 + -1x2)' equal to zero and attempt to solve:

Simplifying
-6 + -1x2 = 0

Solving
-6 + -1x2 = 0

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

Add '6' to each side of the equation.
-6 + 6 + -1x2 = 0 + 6

Combine like terms: -6 + 6 = 0
0 + -1x2 = 0 + 6
-1x2 = 0 + 6

Combine like terms: 0 + 6 = 6
-1x2 = 6

Divide each side by '-1'.
x2 = -6

Simplifying
x2 = -6

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 '(2 + -5x2)' equal to zero and attempt to solve:

Simplifying
2 + -5x2 = 0

Solving
2 + -5x2 = 0

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

Add '-2' to each side of the equation.
2 + -2 + -5x2 = 0 + -2

Combine like terms: 2 + -2 = 0
0 + -5x2 = 0 + -2
-5x2 = 0 + -2

Combine like terms: 0 + -2 = -2
-5x2 = -2

Divide each side by '-5'.
x2 = 0.4

Simplifying
x2 = 0.4

Take the square root of each side:
x = {-0.632455532, 0.632455532}
Solution
x = {-0.632455532, 0.632455532}