21x^3-7x=0

Solution for 21x^3-7x=0 equation:

Simplifying
21x3 + -7x = 0

Reorder the terms:
-7x + 21x3 = 0

Solving
-7x + 21x3 = 0

Solving for variable 'x'.

Factor out the Greatest Common Factor (GCF), '7x'.
7x(-1 + 3x2) = 0

Ignore the factor 7.
Subproblem 1
Set the factor 'x' equal to zero and attempt to solve:

Simplifying
x = 0

Solving
x = 0

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

Simplifying
x = 0
Subproblem 2
Set the factor '(-1 + 3x2)' equal to zero and attempt to solve:

Simplifying
-1 + 3x2 = 0

Solving
-1 + 3x2 = 0

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

Add '1' to each side of the equation.
-1 + 1 + 3x2 = 0 + 1

Combine like terms: -1 + 1 = 0
0 + 3x2 = 0 + 1
3x2 = 0 + 1

Combine like terms: 0 + 1 = 1
3x2 = 1

Divide each side by '3'.
x2 = 0.3333333333

Simplifying
x2 = 0.3333333333

Take the square root of each side:
x = {-0.577350269, 0.577350269}
Solution
x = {0, -0.577350269, 0.577350269}