2x^2-4=21

Solution for 2x^2-4=21 equation:

Simplifying
2x2 + -4 = 21

Reorder the terms:
-4 + 2x2 = 21

Solving
-4 + 2x2 = 21

Solving for variable 'x'.

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

Add '4' to each side of the equation.
-4 + 4 + 2x2 = 21 + 4

Combine like terms: -4 + 4 = 0
0 + 2x2 = 21 + 4
2x2 = 21 + 4

Combine like terms: 21 + 4 = 25
2x2 = 25

Divide each side by '2'.
x2 = 12.5

Simplifying
x2 = 12.5

Take the square root of each side:
x = {-3.535533906, 3.535533906}