-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}