Proving that perfect square is a natural number


Assignment:

Recall that a perfect square is a natural number n such that n = (k^2), for some natural number k.

Theorem. If the natural number n is not a perfect square, then n^(1/2) is irrational.

Proof.
S(1): Suppose n^(1/2) = r/s for some natural numbers r and s.

S(2): We may assume that r and s have no prime factors in common, since any common prime factors may be cancelled.

S(3): From the first step, we have (s^2)*n = r^2.

S(4): Suppose that s>1 and p is a prime factor of s.

S(5): Then p is a prime factor of s^2.

S(6): Hence p is a prime factor of r^2 = (s^2)*n.

S(7): It follows that p is a prime factor of r.

S(8): This contradicts our assumption that r and s have no prime factors in common, and so s = 1.

S(9): Therefore, n = (r^2), so n is a perfect square.

Explain all S(1) ~ S(9)

Provide complete and step by step solution for the question and show calculations and use formulas.

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Algebra: Proving that perfect square is a natural number
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