JEE Main2008MathematicsSets and RelationsActual
Let R be the real line. Consider the following subsets of the plane R R . S= (x, y): y=x+1 and 0 < x < 2 , T= (x, y): x-y is an integer . Which one of the following is true?
Options
- Aneither S nor T is an equivalence relation on R
- Bboth S and T are equivalence relations on R
- CS is an equivalence relation on R but T is not
- DT is an equivalence relation on R but S is not
Correct answer
D. T is an equivalence relation on R but S is not
Step-by-step solution
T= (x, y): x-y l as 0 I T is a reflexive relation. If x-y 1 y-x I T is symmetrical also If x-y=l₁ and y-z=l₂ Then x-z=(x-y)+(y-z)=l₁+I₂ I T is also transitive. Hence T is an equivalence relation. Clearly x x+1 (x, x) S S is not reflexive.