4x^2-1=21

Solution for 4x^2-1=21 equation:

Simplifying
4x2 + -1 = 21

Reorder the terms:
-1 + 4x2 = 21

Solving
-1 + 4x2 = 21

Solving for variable 'x'.

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

Add '1' to each side of the equation.
-1 + 1 + 4x2 = 21 + 1

Combine like terms: -1 + 1 = 0
0 + 4x2 = 21 + 1
4x2 = 21 + 1

Combine like terms: 21 + 1 = 22
4x2 = 22

Divide each side by '4'.
x2 = 5.5

Simplifying
x2 = 5.5

Take the square root of each side:
x = {-2.34520788, 2.34520788}