1.

Let f : N `to N : f(x) =2 x` for all `x in N` Show that f is one -one and into.

Answer» We have
`f(x_(1)) = f(x_(2)) rArr 2x_(1) =2 x_(2) rArr x_(1) = x_(2)`.
`:. ` f is one - one
Let y =2x . Then `x=(y)/(2).`
If we put y=3 then `x=(3)/(2) in N`
Thus `3 in N` has no pre-image in N
`:.` f is into
Hence f is one-one and into .


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