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Surjective functions 
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#1
Mar1011, 02:12 AM

P: 3

1. The problem statement, all variables and given/known data
i) Show explicitly that any noninjective function with a right inverse has another right inverse ii) Give an example of a function which has (at least) two distinct left inverses 2. Relevant equations i) I don't believe there are any. ii) " 3. The attempt at a solution i) Since it says "explicitly" I doubt that my attempt would count as a solution even if it were correct, but here it is; Since the function is noninjective and has a right inverse, it must therefore be surjective as it cannot be bijective, and in order for this function to be surjective it must have at least one more right inverse. I also tried showing first that f(x) = x^3  x is noninjective and then showing that the values x = 1,0,1 map to f(x) = 0 that I would be showing this is true but I am not sure if it is correct. ii) For this I am really not sure if there is an easier way to do it apart from trial and error but I understand the theory behind it. Thanks in advance, SD123 


#2
Mar1011, 04:25 AM

Math
Emeritus
Sci Advisor
Thanks
PF Gold
P: 39,682

Try something as simple as this: f:{a, b, c}> {x, y} defined by f(a)= x,f(b)= x, f(c)= y. g:{x, y}>{a, b, c}, defined by g(x)= a, g(y)= c is a right inverse.
Think about that example to prove (i). However, note that an example is NOT a general proof. 


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