Answer: x+9
Explanation:
My Espanol is a bit bad so I will explain in English,
if you factorize the equation, you get (x+9)^2. This is the area of the shape. A square has 4 sides with similar value. So to get the area, you multiply 2 sides of it together. But in this case, you have to find the side of the square so the answer is x+9... (x+9)(x+9) = x^2+18x+81
De nada