Question

If * is an operation on Q₀, defined by a*b = ab/2, ∀ a, b ∈ Q₀, then identity element of this operation is :

(a) 1

(b) 0

(c) 2

(d) 3

Answer 1

Answer is (c)

If e is identity element

For a ∈ Q₀

a*e = a

⇒ ae/2 = a

e = 2