- #1
ehrenfest
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Homework Statement
I am trying to prove that if the binary operation * is associative, then
[tex]a_1*a_2*...*a_n [/tex]
is unambiguous.
Homework Equations
The Attempt at a Solution
This clearly calls for induction. The base case, n=3, is true by the definition of associativity. Assume that the result is true for n=k. From the induction hypothesis, it is clear that (a_1*...*a_n)*a_{k+1} is unambiguous. It is also clear that a_1*(a_2*...*a_{k+1}) is unambiguous. Because both of these expressions are unambiguous and because we have the n=3 case, we know that
[tex](a_1*...*a_k)*a_{k+1} = (a_1*(a_2*...*a_k))*a_{k+1} = a_1*((a_2*...*a_k)*a_{k+1}) = (a_1*...*a_k)*a_{k+1}[/tex]
So, that shows the result for one very specific case. I cannot think of how to knock out all the cases at once though...
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