Yes, you're right--thanks for pointing that out.  But Maple 12 seems not to have the RationalMapImage command (or RationalMapPreImage), at least when I try to use it.   Is there a way to get around this limitation?

Yes, you're right--thanks for pointing that out.  But Maple 12 seems not to have the RationalMapImage command (or RationalMapPreImage), at least when I try to use it.   Is there a way to get around this limitation?