1.

Show that `f: N to N ` defined by ` f(n) = {[(n)/(2) if n is even ], [(n+1)/(2) if n is odd ]}` is a many -one onto function

Answer» We have
`f(1) =((1 +1) )/(2) = (2)/(2) =1 " and " f(2) =(2)/(2) =1`
Thus `f(1) =f(2) " while " 1 ne 2`
`:.` f is many -one
In order to show that f is onto, consider an arbitrary element `n in N`
If n is odd then `(2n-1)` is odd and
`f( 2n-1) =((2n-1+1))/(2) =(2n)/(2) =n`
If n is even then 2n is even and
` f(2n) =(2n)/(2) =n`
Thus for each `n in N` (whether even or odd ) there exists its pre-image in N.
`:. ` f is onto.
Hence f is many -one onto.


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