Answer:
3 centimeters (not squared!)
Explanation:
Area = lw
You can find it using this formula:
a = √A
A = √9
You would get 3 as your answer.
You can also think of it like this:
Area of a square = lw
What two numbers multiplied together get you 9?
3 x 3 = 9
Hope this helps.
Also, it's just a side length, so don't square it! :)