class 12 maths relations and functions

State whether the following statements are true or false. Justify.

(i) For an arbitrary binary operation $*$ on a set N, a $*$ a $=$ a $\forall a \in Q$

(ii) If $*$ is a commutative binary operation on N, then a$*$ (b$*$ c)$=$ (c $*$ b)$*$ a

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📘 Relations and Functions NCERT Ex. 1.4,Q.12, Page 26 SA

State whether the following statements are true or false. Justify.

(i) For an arbitrary binary operation $*$ on a set N, a $*$ a $=$ a $\forall a \in Q$

(ii) If $*$ is a commutative binary operation on N, then a$*$ (b$*$ c)$=$ (c $*$ b)$*$ a

Official Solution

VVidaara Team ✓ Verified solution NCERT & Exemplar

(i) False.
A binary operation on N is defined as :

a $*$ a $=$ a $\forall a \in Q$. For example, a $*$ b$=$a + b $\forall a,b \in Q$ , then

a $*$ a $=$ a + a $=$ 2a$\ne$a.

Here $' * '$ is not defined.

(ii) True

a $*$(b $*$c)$=$(b $*$c)$*$a $=$(c $*$ b) $*$a. (b $*$c$=$c$*$ b is commutative)

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