Show that a one-one function `f : {1, 2, 3}-> {1, 2, 3}`must be onto.

Explanation

We have given,` f:{1,2,3}->{1,2,3}`

Let `A={1,2,3}`

function `f:A->A`

Function `f:{1,2,3}->{1,2,3}`

Since f is one-one.

(i) `f(1)=1,f(2)=2,f(3)=3`

(ii)` f(1)=1,f(2)=3,f(3)=2`

(iii) `f(1)=2,f(2)=3,f(3)=1`

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