- #1
mehrts
- 15
- 0
Prove that there is a mapping from a set to itself that is one-to one but not onto iff there is a mapping from the set to itself that is onto but not one-to -one.
Since this is a 'iff' proof, so I must prove the statementlike two 'if' statements.
Let g:S ---> S.
Assume that g is 1-1 but not onto.
==> g(x1) = g(x2), for x1,x2 E S
==> x1 = x2
Now what ? Since the mapping is not onto, there must be no y E S such that y = g(x) for some x E S. I'm stuck. Dunno what to do :-(
Since this is a 'iff' proof, so I must prove the statementlike two 'if' statements.
Let g:S ---> S.
Assume that g is 1-1 but not onto.
==> g(x1) = g(x2), for x1,x2 E S
==> x1 = x2
Now what ? Since the mapping is not onto, there must be no y E S such that y = g(x) for some x E S. I'm stuck. Dunno what to do :-(
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