9-4x^2: I don't know where to begin with this one. There are no examples in the book and no odd numbered similar problems so that I could possibly reverse engineer the problem.

12a^2 +24a: for this one I started with12(a+1)(a+2).From there I went on to several different variations but came up empty. Wait... is12a(a+2)the right answer?

Any and all help is much appreciated. Thanks!