@acer Thank you.  Searching "subexpression" brought lots of helpful information.  Jrogn in 90% of the battle sometimes.

@acer Thank you.  I fumble fingered the negative sign but you were correct, I did not realize I made 'a' a function by neglecting the space or a multiplication sign after the 'a'.  Making that change gave me the results I expected.

I think I still have a more general question, is there a way to get Maple to transform a specific term in an expression?