3x^2+6-21=0

Solution for 3x^2+6-21=0 equation:

Simplifying
3x2 + 6 + -21 = 0

Reorder the terms:
6 + -21 + 3x2 = 0

Combine like terms: 6 + -21 = -15
-15 + 3x2 = 0

Solving
-15 + 3x2 = 0

Solving for variable 'x'.

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

Add '15' to each side of the equation.
-15 + 15 + 3x2 = 0 + 15

Combine like terms: -15 + 15 = 0
0 + 3x2 = 0 + 15
3x2 = 0 + 15

Combine like terms: 0 + 15 = 15
3x2 = 15

Divide each side by '3'.
x2 = 5

Simplifying
x2 = 5

Take the square root of each side:
x = {-2.236067978, 2.236067978}