3=2x^2-21

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

Simplifying
3 = 2x2 + -21

Reorder the terms:
3 = -21 + 2x2

Solving
3 = -21 + 2x2

Solving for variable 'x'.

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

Add '-2x2' to each side of the equation.
3 + -2x2 = -21 + 2x2 + -2x2

Combine like terms: 2x2 + -2x2 = 0
3 + -2x2 = -21 + 0
3 + -2x2 = -21

Add '-3' to each side of the equation.
3 + -3 + -2x2 = -21 + -3

Combine like terms: 3 + -3 = 0
0 + -2x2 = -21 + -3
-2x2 = -21 + -3

Combine like terms: -21 + -3 = -24
-2x2 = -24

Divide each side by '-2'.
x2 = 12

Simplifying
x2 = 12

Take the square root of each side:
x = {-3.464101615, 3.464101615}