Prove the following theorems using direct proof, indirect proof(contradiction, contrapositive), counterexample, and/or proof by cases. 1. For every pair of positive real numbers x and y, if xy > 400, then x > 20 or y > 20. 2. For integers x and y. If xy is odd, then x is odd and y is odd.

Prove the following theorems using direct proof, indirect proof(contradiction, contrapositive), counterexample, and/or proof by cases. 1. For every pair of positive real numbers x and y, if xy > 400, then x > 20 or y > 20. 2. For integers x and y. If xy is odd, then x is odd and y is odd.

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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