Determine whether each of the following operations define a binary operation on the given set or not:

‘O’ on Z defined by a O b = ab for all a,b Z.

Given that ‘Ο’ is an operation that is valid in the Integers ‘Z’ and it is defined as given:


aΟb = ab, where a,bZ


Since aZ and bZ,


According to the problem it is given that on applying the operation ‘*’ for two given integers it gives Integers as a result of the operation,


aΟbZ ...... (1)


Let us values of a = 2 and b = – 2 on substituting in the R.H.S side we get,


ab = 2 – 2



abZ ...... (2)


From (2), we can see that ab doesn’t give only Integers as a result. So, this cannot be stated as a binary function.


The operation ‘Ο’ does not define a binary function on Z.


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