-x^2+81=0

Solution for -x^2+81=0 equation:

Simplifying
-1x2 + 81 = 0

Reorder the terms:
81 + -1x2 = 0

Solving
81 + -1x2 = 0

Solving for variable 'x'.

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

Add '-81' to each side of the equation.
81 + -81 + -1x2 = 0 + -81

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

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

Divide each side by '-1'.
x2 = 81

Simplifying
x2 = 81

Take the square root of each side:
x = {-9, 9}