Answer
$ x^2+4x+4-9y^2$.
Work Step by Step
We notice that the given expression contains two factors which can be written as $A+B$ and $A-B$, where $A=x+2$ and $B=3y$..
Use the special formula $(A+B)(A-B)=A^2-B^2$.
$\Rightarrow [(x+2)+3y][(x+2)-3y]=(x+2)^2-(3y)^2$
Use the special formula $(A+B)^2=A^2+2AB+B^2$ to expand $(x+2)^2$, where $A=x$ and $B=2$.
$\Rightarrow = x^2+4x+4-9y^2$.
