That is the right answer anonymous but it is not quite finished. 
I can see just by looking that this will be the difference of 2 squares. This is something that you should recognise.
$$\boxed{(a+b)(a-b)=a^2-b^2}$$
So
$$\\(2x+3)(2x-3) \\
=(2x)^2-3^2\\
=2x^2-9$$
