Decide whether or not the following propositions are true or false. Justify each of your conclusions with a proof or a counterexample. (d) ∃x ∈ R ¬(x 2 < 36) (e) ¬∀x ∈ R (x 2 < 36) (f) ∀x ∈ R ¬(x 2 < 36)
Decide whether or not the following propositions are true or false. Justify each of your conclusions with a proof or a counterexample. (d) ∃x ∈ R ¬(x 2 < 36) (e) ¬∀x ∈ R (x 2 < 36) (f) ∀x ∈ R ¬(x 2 < 36)
Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
Problem 1RQ
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Question
Decide whether or not the following propositions are true or false. Justify each of
your conclusions with a proof or a counterexample.
(d) ∃x ∈ R ¬(x 2 < 36)
(e) ¬∀x ∈ R (x 2 < 36)
(f) ∀x ∈ R ¬(x 2 < 36)
Expert Solution
Step 1
(d) ∃x ∈ R ¬(x2 < 36)
≈ ∃x ∈ R (x2 ≥ 36)
Consider any x ≥6 or x ≤ -6
Then, x2 ≥ 36 => ¬(x2 < 36) becomes true.
For example, for x = 7, x2 = 49 > 36
Hence, the given proposition is True. [Ans]
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