State whether the following statements are true or false. Justify.
(i) For an arbitrary binary operation * on a set N, a*a = a ∀ a ∈N.
(ii) If * is a commutative binary operation on N, then a * (b * c) = (c * b) * a.
Consider a binary operation * on N defined as a * b = a3 + b3 . Choose the correct answer.
(A) Is * both associative and commutative ?
(B) Is * commutative but not associative?
(C) Is * associative but not commutative?
(D) Is * neither commutative nor associative?
A binary operation on a non empty set A is a mapping from A x A → A.
Since A contains two elements
A x A contains 2 x 2 = 4 elements.
If ‘*’ is a binary operation on A. then * : A x A → A can be defined in 24 = 16 ways.
∴ (B) is correct answer.
Let A = Q x Q. Let be a binary operation on A defined by (a, b) * (c, d) = (ac, ad + b).
Then
(i) Find the identify element of (A, *)
(ii) Find the invertible elements of (A, *)
Define binary operation ‘*’ on Q as follows : a * b = a + b – ab, a, b∈ Q
(i) Find the identity element of (Q, *).
(ii) Which elements in (Q. *) are invertible?