First we have to find length of 1 side of the square. We can use formula for area of the square. A=aa ==> \(A=a^2\) where a is length of the side.
From this formula we can find
\(a= \sqrt{A}\)
a=\(\sqrt{6561} =81 - 1 side\)
Now we just have to multiply it by 4, because there are 4 sides.
814=324 - its the answer