1.

A binary operation * on the set (0, 1, 2, 3, 4, 5) is defined as \(a*b=\begin{cases}a+b;\quad if&a+b<6\\a+b-6;\quad if&a+b\geq6\end{cases}\)Show that 0 is the identity for this operation and each element a has an inverse (6 - a)

Answer»

To find: identity and inverse element 

For a binary operation if a*e = a, then e s called the right identity 

If e*a = a then e is called the left identity 

For the given binary operation, 

e*b = b 

⇒ e + b = b 

⇒ e = 0 which is less than 6. 

b*e = b 

⇒ b + e = b 

⇒ e = 0 which is less than 6 

For the 2nd condition, 

e*b = b 

⇒ e + b - 6 = b 

⇒ e = 6 

But e = 6 does not belong to the given set (0,1,2,3,4,5) 

So the identity element is 0 

An element c is said to be the inverse of a, if a*c = e where e is the identity element (in our case it is 0) 

a*c = e 

⇒ a + c = e 

⇒ a + c = 0 

⇒ c = - a 

a belongs to (0,1,2,3,4,5) 

- a belongs to (0, - 1, - 2, - 3, - 4, - 5) 

So c belongs to (0, - 1, - 2, - 3, - 4, - 5) 

So c = - a is not the inverse for all elements a 

Putting in the 2nd condition a*c = e 

⇒ a + c - 6 = 0 

⇒ c = 6 - a 

0≤a<6 ⇒ - 6≤ - a<0⇒ 0≤6 - a<60≤c<5 

So c belongs to the given set 

Hence the inverse of the element a is (6 - a) 

Hence proved



Discussion

No Comment Found

Related InterviewSolutions