Can someone please help me with this question? thanks
A binary operation * is defined on Z by m*n = m + n -2
Prove that Z with operation * is a monoid

Re:To prove that Z becomes a monoid you have to establish three things:

The operation * is defined for any two numbers m and n from Z.

The operation * is associative.

The operation * has a unit e such that for any m in Z m*e = e*m = m.

Exactly which if the three do you find difficult to prove?

i know the monoid properties but how do i relate it with m*n = m + n -2???? i really blur about this....:(

OK. A step at a time.

>The operation * is defined for any two numbers m and n from
>Z.

Is this true? Is the operation * defined for all m and n?