-81=-x^2

Solution for -81=-x^2 equation:

Simplifying
-81 = -1x2

Solving
-81 = -1x2

Solving for variable 'x'.

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

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

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

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

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

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

Simplifying
x2 = 81

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