isPrefix(h:t, L) = isPrefix(t, L)There are many counterexamples. How about h = 1, t = [2], L = [2,2]. The left-hand side of the equation is
isPrefix(1:[2], [2,2]) = isPrefix([1,2], [2,2]) = false since [1,2] is not a prefix of [2,2].The right-hand side of the equation is
isPrefix([2], [2,2]) = true since [2] is a prefix of [2,2].The two sides are not the same for this example.