I'll break this into pieces so you'll see what is happening:
- . This is what the difference of squares is (ring a bell?).
- . The most you can take out from the whole expression (i.e. BOTH terms) is a single . You can't factor out an because the second term does not have one and you can't factor out another because the first term only has one .
- . Not much we can do here but notice how this looks like in the second bullet above? They look similar but are not equal so that you can not directly cancel them. However, (remember this trick), if you factor out a -1 from this expression, we get: which we can now cancel with the other (4x - y).
- . The most you can factor out from both terms is an . The reasoning is the same as the second bullet.
Now, see what you can cancel and hopefully you'll be able to do your other problems similarly as well.