No: compression and expansion are indeed inverse operations, but you do invert an expansion into a contraction by changing the sign, you do so by using the multiplication inverse; basically, whenever you contract by a factorn, you also expand by1/nnot-n, and when you expand byk, you also contract by1/knot-k.

Changing the sign has nothing do with expansions or compressions; in fact, if you touch the sign, you are doing, besides stretching, another transformation: reflection.