Among the relations S = a , b : a , b ∈ R - 0 , 2 + a b > 0 and T = a , b : a , b ∈ R , a 2…

Among the relations
S=a,b:a,bR-0,2+ab>0 and T=a,b:a,bR,a2-b2Z,
  1. S is transitive but T is not
  2. both S and T are symmetric
  3. neither S not T is transitive
  4. T is symmetric but S is not

Solution

Given,

a, b  I and relation T is defined as a2-b2I

Now if a2-b2I so b2-a2 will also be integer, for example if 52-42=9 is integer then 42-52=-9 is also a integer,

Now checking transitive,

If 42-32=7 is an integer, 32-22=5 is an integer then 42-22=12 is also an integer, hence we can say that T is symmetric and transitive,

 Now checking relation S which is defined as 2+ab>0,

So, if we replace ab by -19 then 2+ab>0 is true but we take ba=-9 for symmetric we get 2+ba=2-9=-70 hence, the relation is not symmetric, 

Now checking transitive, now if 2+ab>0ab>-2 and bc>-2 then we cannot say that ac>-2,

For example if we take 41>-2, 1-1>-2 then 4-1-2, hence it is not transitive,

Hence, we can say that  T is symmetric and S is not.

Asked in: JEE Main 2023 (31 Jan Shift 2)

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