Question

List the elements of the following sets:

{x : x = 2y + 5; y ∈ N and 2 ≤ y < 6}

Answer 1

{x : x = 2y + 5; y ∈ N and 2 ≤ y < 6}
x = 2y + 5

When y = 2,
x = 2 x 2+5
= 4+5
= 9

When y = 3,
x = 2 x 3 + 5
= 6+5
= 11

When y = 4,
x = 2 x 4+5
= 8+5
= 13

When y = 5,
x = 2 x 5 + 5
= 10+5
= 15

∴ Elements of the given set {x : x = 2y + 5; y ∈ N and 2≤ y ≤6} are 9, 11, 13, 15