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.
(i) On Z+, define * by a * b = a − b
(ii) On Z+, define * by a * b = ab
(iii) On R, define * by a * b = ab2
(iv) On Z+, define * by a * b = |a − b|
(v) On Z+, define * by a * b = a
For each binary operation * defined below, determine whether * is commutative or associative.
(i) On Z, define a * b = a ā b
(ii) On Q, define a * b = ab + 1
(iii) On Q, define a * b
(iv) On Z+, define a * b = 2ab
(v) On Z+, define a * b = ab
(vi) On R ā {ā1}, define