4. (a) If G and H are graphs with 4 vertices and 3 edges, then G =H. (b) If every vertex of G has degree 2, then G must be a cycle Cn for some n > 3. 5. (a) If a : N + N satisfies the recursion a(n) = a(n 1) + 2, then a(n) = 2n. (b) No Fibonacci number except the number 1 is a perfect square