Here is your answer
Given area is
z^2 + 18z + 81
= z^2 + 2× z × 9 + 9^2
[using (a+b)^2= a^2 + 2ab + b^2], we get
= (z+9)^2
we know that area of a square is represented by side^2.
So, here
Side of square is

HOPE IT IS USEFUL
0 = f(x) = (x - r)(x - s) = x² - (r+s) + rs
We have r=1.5+√2, s=1.5 -√2 so r+s = 3 and
rs = (1.5+√2)(1.5 - √2) = 1.5² - (√2)² = 2.25 - 2 = 0.25
f(x) = x² - 3x + -.25
For integer coefficients we mulitply by 4,
g(x) = 4f(x) = 4x² - 12x - 1
Answer: 4x² - 12x - 1 = 0
If you are reffering to this dot plot, it would be 13 trees being studied.