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    cant believe i cant get my head around this, come to revising and just on a mental block, i know the defintion but cant see where its comming from!

    Let f be a function whose domain is a set A. The function f is injective if for all a and b in A, if f(a) = f(b), then a = b; that is, f(a) = f(b) implies a = b



    i have a question here

    [-1,1] -> [0,1]

    f(x) = (x+2)^(-1)

    is the function injective?

    i know it is, but cant see how exactly im using the definition to show it is, would anyone mind explaining?
    • PS Helper
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    Well suppose (a+2)^{-1} = (b+2)^{-1}. You need to show that this implies that a=b (just rearrange).
 
 
 
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