[QUOTE="nbtrap1212"][QUOTE="loco145"][QUOTE="nbtrap1212"][QUOTE="loco145"][QUOTE="nbtrap1212"]There was nothing wrong with his algebra.
loco145
Yes, there is. If you start with (_)! not defined for 0 you can't do what he did. (0)!=1 Because things wouldn't work otherwise, not big mystery here.Wrong. He assumed that x! is correctly defined for all positive integers and correctly deduced that it implies 0!=1.
Again, what he showed is not the reason 0!=1, but merely an implication of the definition of the factorial function on a positive integer. But it is true that 0!=1.
No.
n! can be defined as (n-1)! * n =n!.
Ok
which can be expressed as n! * (n+1) = (n+1)!
For 0?, why?
Thus, when we plug in n when n = 0, we get
0! = (0+1)!/(0+1)
For 0?, why?
Rest my case.
I think I know what you're getting at.
If "n!*(n+1)=(n+1)! is true for all non-negative integers" is his assumption, then his algebra is correct.
However, n!*(n+1)=(n+1)! is only deducible from the definition of the factorial function on all positive integers (not 0) for n being a positive integer.
In other words, it is impossible to show that 0!=1 from the definition of the factorial function on the set of positive integers alone; one must assume that n!(n+1)=(n+1)! is true for all non-negative integers.
Like I said before, 0!=1 because that is how we have defined it.
That, 0!=1 because that how it was defined. And it was defined because it wouldn't work otherwise. Nothing more. What he did didn't had sense if we don't asume 0!=1 for a start.I wouldn't agree with "it wouldn't work otherwise." But I do agree with your second sentence. Still, his algebra was correct.
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