Prove each of the following statements using a direct proof, a proof by contrapositive, or a proof by contradiction (and cases when needed). For each statement, indicate which proof method you used, as well as the assumptions (what you suppose) and the conclusions (what you need to show) of the proof. A.) The average of any odd integer and any even integer is not an integer. B.) For any integers x and y, if x + y is odd, then x and y have opposite parity. C.) For any real number x, x + |x − ?| ≥ 4

Advanced Engineering Mathematics
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ISBN:9780470458365
Author:Erwin Kreyszig
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Chapter2: Second-order Linear Odes
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Prove each of the following statements using a direct proof, a proof by contrapositive, or a proof by contradiction (and cases when needed). For each statement, indicate which proof method you used, as well as the assumptions (what you suppose) and the conclusions (what you need to show) of the proof.

A.) The average of any odd integer and any even integer is not an integer.
B.) For any integers x and y, if x + y is odd, then x and y have opposite parity.
C.) For any real number x, x + |x − ?| ≥ 4

Definitions:
An integer n is even if and only if there exists an integer k such that n = 2k. An integer n is
odd if and only if there exists an integer k such that n = 2k + 1.
●
●
●
Two integers have the same parity when they are both even or when they are both odd. Two
integers have opposite parity when one is even and the other one is odd.
An integer n is divisible by an integer d with d‡ 0, denoted d | n, if and only if there exists an
integer k such that n = dk.
A real number is rational if and only if there exist integers a and b with b ‡ 0 such that
r = a/b.
For any real numbers x and y, the average of x and y is given by (x + y)/2.
For any real number x, the absolute value of x, denoted [x], is defined as follows:
[x if x ≥ 0
l-x if x < 0
|x| =
Transcribed Image Text:Definitions: An integer n is even if and only if there exists an integer k such that n = 2k. An integer n is odd if and only if there exists an integer k such that n = 2k + 1. ● ● ● Two integers have the same parity when they are both even or when they are both odd. Two integers have opposite parity when one is even and the other one is odd. An integer n is divisible by an integer d with d‡ 0, denoted d | n, if and only if there exists an integer k such that n = dk. A real number is rational if and only if there exist integers a and b with b ‡ 0 such that r = a/b. For any real numbers x and y, the average of x and y is given by (x + y)/2. For any real number x, the absolute value of x, denoted [x], is defined as follows: [x if x ≥ 0 l-x if x < 0 |x| =
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