If the area of a square is 81 what is the length of one side?

Area of a square = side²

81 = side²

√81 = √ (side²0

√81 = side

side = ± 9

Now, the side can never be negative, so the length of one side is 9.

The length of one side is + 9 or 9.

Area of a rectangle = length x width. In a square both sides are equal, so A = x^2. When the A = 81, one side is 9 because 9^2 = 81.