Class 12
Maths :-NCERT Solutions - Relations And Functions
Page No 25:
Question 10:
Find identity a * b = ab/4
Answer:
An element e ∈ Q will be the identity element for the operation * if
a * e = a = e * a, 
a ∈ Q.
We are given
a *
b = ab/4⇒ a*e = a
⇒ae/4=a
⇒ e=4
Similarly, it can be checked for e*a=a, we get e=4Thus, e = 4 is the identity.
