21x^4-19x^2-12=0

Solution for 21x^4-19x^2-12=0 equation:

Simplifying
21x4 + -19x2 + -12 = 0

Reorder the terms:
-12 + -19x2 + 21x4 = 0

Solving
-12 + -19x2 + 21x4 = 0

Solving for variable 'x'.

Factor a trinomial.
(-3 + -7x2)(4 + -3x2) = 0

Subproblem 1
Set the factor '(-3 + -7x2)' equal to zero and attempt to solve:

Simplifying
-3 + -7x2 = 0

Solving
-3 + -7x2 = 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 + -7x2 = 0 + 3

Combine like terms: -3 + 3 = 0
0 + -7x2 = 0 + 3
-7x2 = 0 + 3

Combine like terms: 0 + 3 = 3
-7x2 = 3

Divide each side by '-7'.
x2 = -0.4285714286

Simplifying
x2 = -0.4285714286

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 '(4 + -3x2)' equal to zero and attempt to solve:

Simplifying
4 + -3x2 = 0

Solving
4 + -3x2 = 0

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

Add '-4' to each side of the equation.
4 + -4 + -3x2 = 0 + -4

Combine like terms: 4 + -4 = 0
0 + -3x2 = 0 + -4
-3x2 = 0 + -4

Combine like terms: 0 + -4 = -4
-3x2 = -4

Divide each side by '-3'.
x2 = 1.333333333

Simplifying
x2 = 1.333333333

Take the square root of each side:
x = {-1.154700538, 1.154700538}
Solution
x = {-1.154700538, 1.154700538}