Re: Is this a legitimate proof by induction?

From: Peter L. Montgomery (Peter-Lawrence.Montgomery_at_cwi.nl)
Date: 10/31/04 

Date: Sun, 31 Oct 2004 01:20:35 GMT

In article <3qSdnXrPrYa9qxncRVn-vQ@rogers.com>
"Neil L." <imstr8trippin@yahoo.com> writes:
>Prove for all integers n: 2n + 4 <= (n + 2)!
>
>1. For n = 1, 2(1) + 4 = 6 and (1 + 2)! = 6. Therefore, this formula is
>valid for n = 1.

    But it is false for n = 0, -1.
(n + 2)! is not defined for n = -3, -4, -5 ,...

    If you are assuming n >= 1, then try simplifying the
inequality 2n + 4 <= (n + 2)! by factoring both sides. 

-- 
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