4x^2-1=81

Solution for 4x^2-1=81 equation:

Simplifying
4x2 + -1 = 81

Reorder the terms:
-1 + 4x2 = 81

Solving
-1 + 4x2 = 81

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 = 81 + 1

Combine like terms: -1 + 1 = 0
0 + 4x2 = 81 + 1
4x2 = 81 + 1

Combine like terms: 81 + 1 = 82
4x2 = 82

Divide each side by '4'.
x2 = 20.5

Simplifying
x2 = 20.5

Take the square root of each side:
x = {-4.527692569, 4.527692569}