Relations

If R is a binary relation on a set A define R–1 on A. Let R = {(a, b) : a, b ϵ W and 3a + 2b = 15} and 3a + 2b = 15}, where W is the set of whole numbers. Express R and R–1 as sets of ordered pairs. Show that
(i) dom (R) = range (R–1)
(ii) range (R) = dom (R–1)

Answer : 3a + 2b = 15 a=1 è b=6 a=3 è b=3 a=5 è b=0 R = {(1, 6), (3, 3), (5, 0)} ????−1 = {(6, 1), (3, 3), (0, 5)} The domain of R is the set of first co-ordinates of R Dom(R) = {1, 3, 5} The range...

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Find the domain and range of each of the relations given below: (i) R = {(–1, 1), (1, 1), (–2, 4), (2, 4), (2, 4), (3, 9)}
(ii)R ={(x, y) : x + 2y = 8 and x, y ϵ N}
(iii) R = {(x, y), : y = |x – 1|, x ϵ Z and |x| ≤ 3}

Answer : (i) Given: R = {(–1, 1), (1, 1), (–2, 4), (2, 4), (2, 4), (3, 9)} Dom(R) = {x: (x, y)    R} = {-2, -1, 1, 2, 3} Range(R) = {y: (x, y)    R} = {1, 4, 9}   (ii) Given: R = {(x, y): x +...

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Let A = {a, b, c, d}, B = {c, d, e} and C = {d, e, f, g}. Then verify each of the following identities: (i) A × (B ∩ C) = (A × B) ∩ (A × C) (ii) A × (B – C) = (A × B) – (A × C) (iii) (A × B) ∩ (B × A) = (A ∩ B) × (A ∩ B)

Answer : Given: A = {a, b, c, d,}, B = {c, d, e} and C = {d, e, f, g} Need to prove: A × (B ∩ C) = (A × B) ∩ (A × C) Left hand side, (B ∩ C) = {d, e} ⇒ A × (B ∩ C) = {(a, d), (a, e), (b, d), (b, e),...

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