Theorem (The Principle of Mathematical Induction) For each positive integer n, let P(n) be a statement. If (1) P(1) is true and (2) the implication If P(k), then P(k + 1). is true for every positive integer k, then P(n) is true for every positive integer n. Proof Assume, to the contrary, that the theorem is false. Then conditions (1) and (2) are satisfied but there exist some positive integers n for which P(n) is a false statement. Let S = {n EN: P(n) is false}. Since S is a nonempty subset of N, it follows by the Well-Ordering Principle that S con- tains a least element s. Since P(1) is true, 1 # S. Thus, s≥ 2 and s − 1 € N. Therefore, s – 1 Sand so P(s − 1) is a true statement. By condition (2), P(s) is also true and so s & S. This, however, contradicts our assumption that s € S.

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Please explain the proof in more detail step by step, I really dont understand a word of it.

Theorem
(The Principle of Mathematical Induction) For each positive integer n, let P(n) be a
statement. If
(1) P(1) is true and
(2)
the implication
If P(k), then P(k + 1).
is true for every positive integer k,
then P(n) is true for every positive integer n.
Proof Assume, to the contrary, that the theorem is false. Then conditions (1) and (2) are satisfied
but there exist some positive integers n for which P(n) is a false statement. Let
S = {n EN: P(n) is false}.
Since S is a nonempty subset of N, it follows by the Well-Ordering Principle that S con-
tains a least element s. Since P(1) is true, 1 # S. Thus, s ≥ 2 and s - 1 € N. Therefore,
s - 1 S and so P(s − 1) is a true statement. By condition (2), P(s) is also true and so
s & S. This, however, contradicts our assumption that s € S.
Transcribed Image Text:Theorem (The Principle of Mathematical Induction) For each positive integer n, let P(n) be a statement. If (1) P(1) is true and (2) the implication If P(k), then P(k + 1). is true for every positive integer k, then P(n) is true for every positive integer n. Proof Assume, to the contrary, that the theorem is false. Then conditions (1) and (2) are satisfied but there exist some positive integers n for which P(n) is a false statement. Let S = {n EN: P(n) is false}. Since S is a nonempty subset of N, it follows by the Well-Ordering Principle that S con- tains a least element s. Since P(1) is true, 1 # S. Thus, s ≥ 2 and s - 1 € N. Therefore, s - 1 S and so P(s − 1) is a true statement. By condition (2), P(s) is also true and so s & S. This, however, contradicts our assumption that s € S.
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