Answer
The area of the square is $121y^2+198y+81$ square units.
Work Step by Step
RECALL:
The area of a square is given by the formula $A=s^2$ where s = side length.
The square has $s=11y+9$. Use the formula above to have:
$\\A=(11y+9)^2$
RECALL: $(a+b)^2=a^2+2ab+b^2$
Use the formula above with $a=11y$ and $b=9$ to have:
$\\A=(11y)^2+2(11y)(9)+9^2
\\A=121y^2+198y+81$
