# Mathematical induction

1. Dec 5, 2003

### evil1

Induction Hypothesis:

In fact pa is true for all integers n greater than a particular base value and you should complete the proof given below to use the principle of mathematical induction to prove this.

pa : n-2 < (n^2 – 3n)/12

Base case is n = 14
Because: n-2 < (n^2 – 3n)/12
14-2 < (196-42)/12
12 < 154/12
12 < 12.83

Inductive step
Inductive Hypothesis : Assume pa(k) is true for k > 14. Thus k-2 <(k^2 – 3k)/12.

We must prove that pa(k+1) is true i.e. that (k+1)-2 < ((k+1)^2 – 3(k+1))/12

Now to prove such an inequality we always start with the more complicated side:
((k+1)^2 – 3(k+1))/12 = (k^2 + 2k +1 – 3k – 3)/12

= (k^2 – 3k)/12 + (2k-2)/12

> ....?... + (2k-2)/12 ____because

> ......??......... because

the dotted white line need to be filled in and the because u have to give reasons....

This is the question i have been given to do although no idea on how to finish it any ideas anyone ?

thanks

ok i changed it to 14 although not sure yet on how to finish it, this for me is just baffling

Last edited: Dec 7, 2003
2. Dec 7, 2003

### KLscilevothma

It should be "Assume pa(k) is true for some k >= 14 "

What does the induction hypothesis tell you ?