Factoring Challenge Problems

Sometimes the best way to simplify a really messy expression is to factor it (not multiply it out).  
example:  
The first edition of the textbook had problems like this in section R.6. This edition has taken those problems out, but all the other textbooks we have used in the past have had problems like this and since the departmental final is not based on a particular textbook, it still can have problems like this (in fact the final my students got last semester had a problem of this nature.)  Therefore it is important that you can handle these problems.
Following are some problems that were in the first edition.
Factor and simplify:
  1. a-2b5 - a3b-5
  2. x-1/3y3/4 - x2/3y-1/4
  3. (2x - 3)-3(x + 1)5/4 + (2x - 3)-2(x + 1)1/4







Answers:  1.)  2.)  3.)