JEE Main 2018 — Sets And Relations Question with Solution
From: JEE Main 2018 (Online) 16th April Morning Slot
Question
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 :
Choose an option
Show full solutionCorrect option: B
Correct answer
BRange of R2 is {1, 2, 3, 4}.
Step-by-step explanation
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 =
R2 is not symmetric and transitive
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 =
R2 is not symmetric and transitive
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