Let R be a relation from N to N defined by R =

Question:

Let R be a relation from N to N defined by R = [(ab) : ab ∈ N and a = b2].

Are the following statements true?

(i) (aa) ∈ R for all a ∈ N

(ii) (ab) ∈ R ⇒ (ba) ∈ R

(iii) (ab) ∈ R and (bc) ∈ R ⇒ (ac) ∈ R

Solution:

Given: R = [(ab) : ab ∈ N and a = b2]

(i) (aa) ∈ R for all a ∈ N.

Here $2 \in \mathrm{N}$ hut? $\neq 2^{2}$

$\therefore(2,2) \notin \mathrm{R}$

False

(ii) $(a, b) \in \mathrm{R} \Rightarrow(b, a) \in \mathrm{R}$

$\because 4=2^{2}$

$(4,2) \in \mathrm{R}$, but $(2,4) \notin \mathrm{R}$

False

(iii) $(a, b) \in \mathbf{R}$ and $(b, c) \in \mathbf{R} \Rightarrow(a, c) \in \mathbf{R}$

$\because 16=4^{2}$ and $4=2^{2}$

$\therefore(16,4) \in \mathrm{R}$ and $(4,2) \in \mathrm{R}$

Here,

$(16,2) \notin \mathrm{R}$

False

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