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    				| 1. | 
                                    Let N be the set of all natural number , Z be the set of all integers and sigma : N to Zbe difinedby{:sigma(n)={((n)/(2)",",if,n" is even"),(,,"then"),(-(n-1)/(2)",",if,n" is odd"):} | 
                            
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Answer»  `SIGMA`is ONTO not ONE-one  | 
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