MATH1061/7861, Wed 16 Sep 2020
Question 1. True or false? If x1, x2, x3, … is any infinite sequence, then {x1, x2, x3, …} must be:
A. Finite
B. Infinite
C. Countable
D. Uncountable
E. Countably infinite
NO
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Question 4. Show that N × N × N is countable.
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Question 5. Draw an arrow diagram for the relation 𝜌 on {0,1,2,3,4,5,6} defined by x𝜌y if and only if xy ≡ 1 (mod 7). Is this relation reflexive? Symmetric? Transitive?
(The arrow diagram will be drawn here during during the lecture.)
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