Thanks everyone, that was pretty much what I had expected. I am teaching both to the students but now know how I want to assess them to mirror what they might expect on the diploma. Is it just me or do you find it odd that the expectation is that students only need to do x-a. I suppose this is the more practical application of factoring a cubic or quartic polynomial but I would expect things to be more difficult in this area. Regardless, I think I will allow students to use either method as we move forward.

Thanks everyone again

Dan