3. Prove or give a counterexample to the following: For a set A and
binary relation R on A, if R is reflexive and symmetric, then R must
be transitive as well.
1. Prove the following formulas for all positive integers n.
a) 1 + 2 + 3 + 4 + 5 +...+ n = n(n + 1) :2
b) 1 + 4 + 9 + 16 + 25 + ...+ n2 = n(n + 1)(2n + 1) :6
c) 22n - 1 is a multiple of 3