The relation R defined on the set A={1,2,3,4,5} as R={(a,b):|a2−b2|<16} has cardinality equal to
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Solution
(a,b)∈R⟺|a2−b2|<16 a=1⇒|1−b2|<16⇒b=1,2,3,4 a=2⇒|4−b2|<16⇒b=1,2,3,4 a=3⇒|9−b2|<16⇒b=1,2,3,4 a=4⇒|16−b2|<16⇒b=1,2,3,4,5 a=5⇒|25−b2|<16⇒b=4,5
∴ Total number of elements =19