MATH221 – Mathematics for Computer Science – Autumn 2022
Assignment One – Due Week 6 Friday 5:00pm
Student Name: Student Number:
Tutorial Day & Time:
Question 1. [4 marks]
(a) Let p and q be statements. Write down a compound statement that uses only {∧,∨,∼} (not necessarily all ofthem) and is true only when both p and q have the same truth value. Justify your answer using a truth table.
(b) Is ∼ q ⇒ q ∧ (p ∨∼ q) a tautology, fallacy or contingent statement? Justify your answer.
Question 2. [2 marks] Prove that for every natural number n, the number 4 + n + n2 is not prime.
Question 3. [3 marks] Using the substitution and logical equivalence laws, prove the following equivalence. Donot use a truth table.
p ↔ q ≡ (∼ q ∨p)∧ (∼ p∨ q)
Question 4. [2 marks] Prove or disprove the validity of the following argument.
If Scott Morrison is re-elected, the majority of Australians will not be happy.
Scott Morrison is not re-elected.
Therefore, most Australians are happy.
Question 5. [4 marks] Prove by mathematical induction that 12 + 32 + 52 + · · ·+ (2n−1)2 = 4n3−n3
for
all n ∈ N.