case absolute(x) = x when x >= 0 case absolute(x) = -x
absdiff(x,y) = absolute(x - y)
f(u,v,w) = absdiff(u,v) + absdiff(v,w)You know that absolute(x) computes |x| and absdiff(x,y) computes |x - y|. Do an evaluation of f(3,5,9). Use the rule that you skip directly to the answer for functions that are not the one you are testing.