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QJEEM18Ma708a: JEE Main 2018 Mathematics - Class 11 JEEM18Ma708a Solution: Let N denote the set of all natural numbers. Define two binary…

Let N denote the set of all natural numbers. Define two binary relations on N as R = {(x, y) ∈ N × N : 2x + y = 10} and R2 = {(x, y) ∈ N × N : x + 2y = 10}. Then :

Multiple Choice Options

  • A Range of R1 is {2, 4, 8).
  • B Range of R2 is {1, 2, 3, 4}.
  • C Both R1 and R2 are symmetric relations.
  • D Both R1 and R2 are transitive relations.

Step-by-Step Verified Solution

For R1; 2x + y = 10 and x, y ∈ N possible values for x and y are :

x = 1, y = 8    i.e.   (1, 8);

x = 2, y = 6    i.e    (2, 6);

x = 3, y = 4    i.e    (3, 4);

x = 4, y = 2    i.e    (4, 2)

∴ R1 = { (1, 8), (2, 6), (3, 4), (4, 2) }

∴ Range of R1 is {2, 4, 6, 8}

R1 is not symmetric.

R1 is not transitive also as

(3, 4), (4, 2) ∈ R , but (3, 2) ∉ R1

For R2 : x + 2y = 10 and x, y ∈ N

Possible values of x, and y are :

x = 8, y= 1    i.e    (8, 1)

x = 6, y = 2    i.e    (6, 2)

x = 4, y = 3    i.e    (4, 3) and

x = 2, y = 4    i.e    (2, 4)

∴ R2 = {(8, 1) (6, 2) (4, 3) (2, 4)}

∴ Range of R2 = {1,2,3,4}

R2 is not symmetric and transitive

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