Prove the second piece of Proposition 2.4.10 that if a and b are coprime, and if a | bc, then a | c. (Hint: use the Bezout identity again. Later you will have the opportunity to prove this with more powerful tools; see Exercise 6.6.6.) Proposition 2.4.10. Here are two interesting facts about coprime integers a and b: • If a cand b | c, then ab | c. • If a | bc, then a c.