Answer
$x^2+4x+4-9y^2 $.
Work Step by Step
Use the special-product formula shown below.
$(A+B)\cdot (A-B)=A^2-B^2$
We have $A=(x+2)$ and $B=3y$.
$\Rightarrow [(x+2)+3y][(x+2)-3y]=(x+2)^2-(3y)^2 $
We will expand the expressions on the right hand side.
$(x+2)^2-(3y)^2 $
Use the formula for the square of a binomial.
$(A+B)^2=A^2+2AB+B^2$
We have $A=x$ and $B=2$.
$=x^2+4x+4-9y^2 $.
