3x^2-21=0

Solution for 3x^2-21=0 equation:

Simplifying
3x2 + -21 = 0

Reorder the terms:
-21 + 3x2 = 0

Solving
-21 + 3x2 = 0

Solving for variable 'x'.

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

Add '21' to each side of the equation.
-21 + 21 + 3x2 = 0 + 21

Combine like terms: -21 + 21 = 0
0 + 3x2 = 0 + 21
3x2 = 0 + 21

Combine like terms: 0 + 21 = 21
3x2 = 21

Divide each side by '3'.
x2 = 7

Simplifying
x2 = 7

Take the square root of each side:
x = {-2.645751311, 2.645751311}