Example 27 let the operation * 1s defined on the set of real number r as follows: a*b=|a-b| for all a, b er prove that is a commutative binary operation on r bu

Example 27 Let the operation * 1S defined on the set of real number R as follows: a*b=|a-b| for all a, b eR Prove that Is a commutative binary operation on R but (R, *) is not a semigroup.