Discrete Mathematics

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Module 2: Mathematical Induction & Counting Techniques.

  1. 1c. What is the induction hypothesis assumption for the inequality m! > 2^m where m \ge 4? (i) For m=k, k+1! > 2^k holds (ii) For m=k, k! > 2^k holds (iii) For m=k, k! > 3^k holds (iv) For m=k, k! > 2^{k+1} holds20222m

    Module 2: Mathematical Induction & Counting Techniques.

    What is the induction hypothesis assumption for the inequality m!>2mm! > 2^m where m4m \ge 4?

    (i) For m=km=k, k+1!>2kk+1! > 2^k holds
    (ii) For m=km=k, k!>2kk! > 2^k holds
    (iii) For m=km=k, k!>3kk! > 3^k holds
    (iv) For m=km=k, k!>2k+1k! > 2^{k+1} holds

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  2. 4b. Find the greatest common divisor of 414 and 662 using the Euclidean algorithm.20224m

    Module 2: Mathematical Induction & Counting Techniques.

    Find the greatest common divisor of 414 and 662 using the Euclidean algorithm.

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  3. 4c. If a and b are positive integers, then prove that there exists integers s and t such that \text{gcd}(a, b) = sa + tb.20225m

    Module 2: Mathematical Induction & Counting Techniques.

    If aa and bb are positive integers, then prove that there exists integers ss and tt such that gcd(a,b)=sa+tb\text{gcd}(a, b) = sa + tb.

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  4. 5. Prove the following by using the principle of mathematical induction for all n \in N: 1^3 + 2^3 + 3^3 + \dots + n^3 = \left(\frac{n(n+1)}{2}\right)^2202314m

    Module 2: Mathematical Induction & Counting Techniques.

    Prove the following by using the principle of mathematical induction for all nNn \in N:
    13+23+33++n3=(n(n+1)2)21^3 + 2^3 + 3^3 + \dots + n^3 = \left(\frac{n(n+1)}{2}\right)^2

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  5. 5a. Use mathematical induction to prove this formula for the sum of a finite number of terms of a geometric progression with initial term a and common ratio r: \sum_{j=0}^{n} ar^j = a + ar + ar^2 + \dots + ar^n = \frac{ar^{n+1} - a}{r-1} when $r e 1 where n$ is a non-negative integer.20227m

    Module 2: Mathematical Induction & Counting Techniques.

    Use mathematical induction to prove this formula for the sum of a finite number of terms of a geometric progression with initial term aa and common ratio rr:
    j=0narj=a+ar+ar2++arn=arn+1ar1\sum_{j=0}^{n} ar^j = a + ar + ar^2 + \dots + ar^n = \frac{ar^{n+1} - a}{r-1}
    when $r
    e 1where where n$ is a non-negative integer.

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  6. 6. State and prove Division algorithm theorem well-ordering principle.202314m

    Module 2: Mathematical Induction & Counting Techniques.

    State and prove Division algorithm theorem well-ordering principle.

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  7. 6a. An odd number of people stand in a yard at mutually distinct distances. At the same time each person throws a pie at their nearest neighbour, hitting this person. Use mathematical induction to show that there is at least one survivor, that is, at least one person who is not hit by a pie.20227m

    Module 2: Mathematical Induction & Counting Techniques.

    An odd number of people stand in a yard at mutually distinct distances. At the same time each person throws a pie at their nearest neighbour, hitting this person. Use mathematical induction to show that there is at least one survivor, that is, at least one person who is not hit by a pie.

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  8. 6b. Prove Bernoulli's inequality that if h > -1, then 1+nh \le (1+h)^n for all non-negative integers n.20227m

    Module 2: Mathematical Induction & Counting Techniques.

    Prove Bernoulli's inequality that if h>1h > -1, then 1+nh(1+h)n1+nh \le (1+h)^n for all non-negative integers nn.

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  9. 7a. What is pigeonhole principle? Using it, prove the following: (a) During a month with 30 days, a baseball team plays at least one game a day, but no more than 45 games. Show that there must be a period of some number of consecutive days during which the team must play exactly 14 games.20227m

    Module 2: Mathematical Induction & Counting Techniques.

    What is pigeonhole principle? Using it, prove the following:

    (a) During a month with 30 days, a baseball team plays at least one game a day, but no more than 45 games. Show that there must be a period of some number of consecutive days during which the team must play exactly 14 games.

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  10. 7b. A grocery store employee is stocking apples. Each apple is a different color. There are 10 apples left in the box and the employee pulls out 2 of them at random. What is the probability that the employee pulls out one pink apple and yellow apple?20237m

    Module 2: Mathematical Induction & Counting Techniques.

    A grocery store employee is stocking apples. Each apple is a different color. There are 10 apples left

    in the box and the employee pulls out 2 of them at random. What is the probability that the employee

    pulls out one pink apple and yellow apple?

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  11. 7b. The sequence 8, 11, 9, 1, 4, 6, 12, 10, 5, 7 contains 10 terms. Note that 10 = 3^2 + 1. There are four strictly increasing subsequences of length four, namely, 1, 4, 6, 12; 1, 4, 6, 7; 1, 4, 6, 10; and 1, 4, 5, 7. There is also a strictly decreasing subsequence of length four, namely, 11, 9, 6, 5.20227m

    Module 2: Mathematical Induction & Counting Techniques.

    The sequence 8,11,9,1,4,6,12,10,5,78, 11, 9, 1, 4, 6, 12, 10, 5, 7 contains 10 terms. Note that 10=32+110 = 3^2 + 1. There are four strictly increasing subsequences of length four, namely, 1,4,6,121, 4, 6, 12; 1,4,6,71, 4, 6, 7; 1,4,6,101, 4, 6, 10; and 1,4,5,71, 4, 5, 7. There is also a strictly decreasing subsequence of length four, namely, 11,9,6,511, 9, 6, 5.

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