InterviewSolution
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Let A = {2, 3, 5, 7}. Examine whether the statements given below are true or false.(i) ∃ x ∈ A such that x + 3 > 9.(ii) ∃ x ∈ A such that x is even.(iii) ∃ x ∈ A such that x + 2 = 6.(iv) ∀ x ∈ A, x is prime.(v) ∀ x ∈ A, x + 2 < 10.(vi) ∀ x ∈ A, x + 4 ≥ 11 |
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Answer» Given: A = {2, 3, 5, 7} (i) ∃ x ∈ A such that x + 3 > 9. We have to check whether there exists ‘x’ which belongs to ‘A’, such that x + 3 > 9. When x = 7 ∈ A, x + 3 = 7 + 3 = 10 > 9 So, ∃ x ∈ A and x + 3 > 9. So, the given statement is TRUE. (ii) ∃ x ∈ A such that x is even. We have to check whether there exists ‘x’ which belongs to ‘A’, such that x is even. x = 2, is an even number and 2 ∈ A. So, the given statement is TRUE. (iii) ∃ x ∈ A such that x + 2 = 6. We have to check whether there exists ‘x’ which belongs to ‘A’, such that x + 2 = 6. At x = 2 ⇒ x + 2 = 4 ≠ 6 At x = 3 ⇒ x + 2 = 5 ≠ 6 At x = 5 ⇒ x + 2 = 7 ≠ 6 At x = 7 ⇒ x + 2 = 9 ≠ 6 None of the values satisfy the equation. So, the given statement is FALSE. (iv) ∀ x ∈ A, x is prime. We have to check whether for all ‘x’ which belongs to ‘A’, such that x is a prime number. All ‘x’ which belongs to A = {2, 3, 5, 7} is a prime number. All are prime numbers. So, the given statement is TRUE. (v) ∀ x ∈ A, x + 2 < 10. We have to check whether for all ‘x’ which belongs to ‘A’, such that x + 2 < 10. A = {2, 3, 5, 7} At x = 2 ⇒ x + 2 = 4 < 10 At x = 3 ⇒ x + 2 = 5 < 10 At x = 5 ⇒ x + 2 = 7 < 10 At x = 7 ⇒ x + 2 = 9 < 10 ∀ x ∈ A, x + 2 < 10, is a TRUE statement. (vi) ∀ x ∈ A, x + 4 ≥ 11. We have to check whether for all ‘x’ which belongs to ‘A’, such that x + 4 ≥ 11. A = {2, 3, 5, 7} At x = 2 ⇒ x + 4 = 6 ≥ 11 At x = 3 ⇒ x + 4 = 7 ≥ 11 At x = 5 ⇒ x + 4 = 9 ≥ 11 At x = 7 ⇒ x + 4 = 11 ≥ 11 Only for x = 7, statement is true. ∀ x ∈ A, x + 4 ≥ 11, is a FALSE statement. |
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