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Let A be the set of all 50 students of...

Let `A` be the set of all 50 students of class `X I I` in a central school. Let `f: A->N` be a function defined by `f(x)=`Roll number of student `x` Show that `f` is one-one but not onto.

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`f(x)`=Roll number of students x
For,One one
`f(x1)`=roll number of students `x1`
`f(x2)`=roll number of students `x2`
Putting `f(x1)=f(x2)`
Since no two students of a class can have same roll number
So, f is one one ...
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