Determine whether or not each of the definition of ∗ given below gives a binary operation. In the event that ∗ is not a binary operation, give justification for this.
(iii) On R, defined ∗ by a∗b=ab2
On R, defined ∗ by a∗b=ab2
It is seen that for each a,b∈R, there is a unique element ab2 in R.
This means that ∗ carries each pair (a,b) to a unique element a∗b=ab2 in R. Therefore, ∗ is binary operation.