Linear maps satisfy both conditions L1 and L2 below. I have to find a map R^2 -> R that satisfies ONLY L2 and not L1. I have been thinking about this for quite a while, but I haven't made that much progress. Do I have to use absolute values in some way?

It would be nice to see the actual solution or at least get some clear hints.

xandyare vectors.

L1: f(x+y) = f(x) + f(y)

L2: af(x) = f (ax)