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November 28th, 2017, 10:51 AM   #1
Joined: Oct 2017
From: Rumba

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Proof by induction

Would i be ok to use base step as n = 1 for a function A -> B for one in A

A (x) mapping to B (a1,a2,a3.... am)

No of functions possible for n-1 is m^n

I dont know how to go on with the induction step any ideas?

Last edited by sita; November 28th, 2017 at 10:57 AM.
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November 28th, 2017, 11:05 AM   #2
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To prove by weak mathematical induction the proposition

$P(n) \text { is true for any } n \in \mathbb N^+$,

first prove $P(1) \text { is true.}$ This is frequently very easy to do.

Moreover it justifies the following statement:

$\exists \text { at least one number } k \in \mathbb N^+ \text { such that } P(k) \text { is true.}$

This is frequently called the assumption step although it is clearly a true statement. Notice however, that you may NOT assume that k = 1. You may assume that $k \ge 1.$

Now prove in the second step that

$P(k + 1) \text { is true.}$

What is the intuition?

P(1) is true by the first step so P(1 + 1) = P(2) is true by the second step, so P(2 + 1) = P(3) is true by the second step, so P(3 + 1) = P(4) is true by the second step, and so on forever.

Last edited by JeffM1; November 28th, 2017 at 11:08 AM.
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