Mathematical Induction and Proofs 1. [1 point] Show that a21 is divisible by 8 for all odd a 's. 2. [1 point] Show that every positive integer can be written as a sum of some powers of 2 . 3. [1 point] Show that S1(S2S3)=(S1S2)(S1S3) 4. [1 point] What part of the following argument is wrong and why? 0=020=302=3