# Well-Ordering and Division Theorem

32. Show that there is no rational number b/a whose square is 2, as follows: if b^2 = 2a^2, then b is even, so b = 2c, so, substituting and cancelling 2, 2c^2 = a^2. Use that argument and well-ordering to show that there can be no natural number a > 0 with b^2 = 2a^2 for some natural number b.

33. Let m be the least common multiple of a and b, and let c be a common multiple of a and b. Show that m divides c. Hint: use the division theorem on m and c, and show that the remainder r is a common multiple of a and b, hence r = 0.

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Let's us review the concept of well ordering principle: if a subset of integers is bounded below, then it has a ...

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The solution contains a brief review on the well ordering principle and an outline for the proof.