81=y^2

Solution for 81=y^2 equation:

Simplifying
81 = y2

Solving
81 = y2

Solving for variable 'y'.

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

Add '-1y2' to each side of the equation.
81 + -1y2 = y2 + -1y2

Combine like terms: y2 + -1y2 = 0
81 + -1y2 = 0

Add '-81' to each side of the equation.
81 + -81 + -1y2 = 0 + -81

Combine like terms: 81 + -81 = 0
0 + -1y2 = 0 + -81
-1y2 = 0 + -81

Combine like terms: 0 + -81 = -81
-1y2 = -81

Divide each side by '-1'.
y2 = 81

Simplifying
y2 = 81

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