Let 𝐀 = {𝟑,𝟒,𝟕,𝟖} and 𝐁 = {𝟏,𝟕,𝟏𝟎}. Which of the following sets are relations from 𝐀 to 𝐁?
(i) 𝐑𝟏 ={(𝟑,𝟕), (𝟒,𝟕), (𝟕,𝟏𝟎), (𝟖,𝟏)}
(ii) 𝐑𝟐 = {(𝟑,𝟏), (𝟒,𝟏𝟐)}
(iii) 𝐑𝟑 = {(𝟑,𝟕), (𝟒,𝟏𝟎), (𝟕,𝟕), (𝟕,𝟖), (𝟖,𝟏𝟏), (𝟖,𝟕), (𝟖,𝟏𝟎)}.
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Solution
(i) We note that, R1⊆A×B.
Thus R1 is a relation from A to B.
(ii) Here, (4,12)∈R2, but (4,12)∉A×B.
So, R2 is not a relation from A to B.
(iii) Here, (7,8)∈R3, but (7,8)∉A×B.
So, R3 is not a relation from A to B.