Practicing Success

Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Relations and Functions

Question:

Which of the following sets is not finite?

Options:

$\{(x, y): x^2 + y^2 ≤ 1≤x+y, x, y ∈ R\}$

$\{(x, y): x^2 + y^2 ≤1 ≤ x + y, x, y ∈ Z\}$

$\{(x, y): x^2 ≤ y ≤ |x|, x, y ∈ Z\}$

$\{(x, y): x^2 + y^2 = 1, x, y ∈ Z\}$

Correct Answer:

$\{(x, y): x^2 + y^2 ≤ 1≤x+y, x, y ∈ R\}$

Explanation:

The set $\{(x, y): x^2 + y^2 ≤1≤x+y, x, y ∈ R\}$ consists of all point in the first quadrant which lie inside the circle $x^2 + y^2 = 1$ and above the line $x + y = 1$. So, it is not a finite set.

We have, $\{(x, y): x^2 + y^2 ≤1≤x+y, x, y ∈ R\} = \{(1, 0), (0, 1)\}$.

So, it is a finite set.

Clearly, $\{(x, y): x^2 ≤ y ≤ |x|, x, y ∈ Z\} = \{(0, 0), (1, 1), (-1, 1)\}$ which is a finite set.

We have,

$\{(x, y): x^2 + y^2 = 1, x, y ∈ Z\} = \{(1, 0), (0, 1), (-1, 0), (0, -1)\}$ which is a finite set.