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Question
Determine whether or not the definition of * given below gives a binary operation. In the event that * is not a binary operation give justification of this.
On Z+, define * by a * b = a
Here, Z+ denotes the set of all non-negative integers.
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Solution
\[a, b \in Z^+ \]
\[ \Rightarrow a \in Z^+ \]
\[ \Rightarrow a * b \in Z^+ \]
\[\text{Therefore},\]
\[a * b \in Z^+ , \forall a, b \in Z^+ \]
\[Thus, * \text{ is a binary operation on } Z^+ .\]
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