Prove the following statements using direct, contrapositive, or contradiction proof. a.  Suppose x is an integer. Then x is odd if and only if 3x + 6 is odd. b.  Suppose a, and b are integers. Prove that a is equivalent to b(mod 10) if and only if a is equivalent to b(mod 2) and a is equivalent to b (mod 5). c.  If a is an integer, then a^3 is equivalent to a(mod 3). d. There exists an integer n for which 11 | [(2^n) - 1].

Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter1: Fundamental Concepts Of Algebra
Section1.2: Exponents And Radicals
Problem 85E
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Prove the following statements using direct, contrapositive, or contradiction proof.

a.  Suppose x is an integer. Then x is odd if and only if 3x + 6 is odd.

b.  Suppose a, and b are integers. Prove that a is equivalent to b(mod 10) if and only if a is equivalent to b(mod 2) and a is equivalent to b (mod 5).

c.  If a is an integer, then a^3 is equivalent to a(mod 3).

d. There exists an integer n for which 11 | [(2^n) - 1].

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