>>14167114Nah, that's if it's the other way around. If things substitute each other the curve is concave.
So basically it's like this (sorry for the crude sketch), you compare 2 good X and Y, the green line is your budget. The red curves are retarded because you aren't getting as much as you could and the blue ones are optimal.
If with a convex curve and ideal set up makes the goods basically mutually exclusive.
