4=81x^2

Solution for 4=81x^2 equation:

Simplifying
4 = 81x2

Solving
4 = 81x2

Solving for variable 'x'.

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

Add '-81x2' to each side of the equation.
4 + -81x2 = 81x2 + -81x2

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

Add '-4' to each side of the equation.
4 + -4 + -81x2 = 0 + -4

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

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

Divide each side by '-81'.
x2 = 0.04938271605

Simplifying
x2 = 0.04938271605

Take the square root of each side:
x = {-0.222222222, 0.222222222}