0.81-x^2=0

Solution for 0.81-x^2=0 equation:

Simplifying
0.81 + -1x2 = 0

Solving
0.81 + -1x2 = 0

Solving for variable 'x'.

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

Add '-0.81' to each side of the equation.
0.81 + -0.81 + -1x2 = 0 + -0.81

Combine like terms: 0.81 + -0.81 = 0.00
0.00 + -1x2 = 0 + -0.81
-1x2 = 0 + -0.81

Combine like terms: 0 + -0.81 = -0.81
-1x2 = -0.81

Divide each side by '-1'.
x2 = 0.81

Simplifying
x2 = 0.81

Take the square root of each side:
x = {-0.9, 0.9}