Number Theory Fundamentals

From the study guide

Course Outline

  1. Division Algorithm
  2. Divisibility and Linear Combinations
  3. Quotients and Remainders
  4. Modular Arithmetic
  5. Prime Factorization
  6. Prime Numbers and Theorems
  7. Greatest Common Divisor
  8. Euclid's Algorithm
  9. Extended Euclidean Algorithm
  10. Multiplicative Inverse

1. Division Algorithm

Key Concepts & Definitions

  • Division Algorithm:
    The theorem stating that for any integer aa and positive integer dd, there exist unique integers qq (quotient) and rr (remainder) such that:
    $ a = dq + r \quad \text{with} \quad 0 \leq r < d $
    This guarantees the existence and uniqueness of the quotient and remainder when dividing integers.

  • Quotients and Remainders:
    The results of division, where the quotient qq is the integer part of the division, and the remainder rr is what is left over, satisfying 0≤r<d0 \leq r < d.

  • Integer Division Definitions:
    In the context of the Division Algorithm, the quotient qq and remainder rr are defined such that:
    $ a = dq + r $ with the specified bounds on rr. The quotient and remainder are uniquely determined by this relation.

  • Procedural Version of the Division Algorithm:
    A step-by-step method to compute qq and rr for given integers aa and positive integer dd. It involves iterative subtraction or division steps to find the unique qq and rr satisfying the relation, ensuring 0≤r<d0 \leq r < d.

Essential Points

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Practice quiz preview

1. What is the primary role of the division algorithm in number theory?

2. Who is credited with formulating the theorem that if a number divides two integers, then it divides any linear combination of those integers?

3. How do the quotient and remainder of a division fundamentally differ from each other?

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Flashcard preview

Division Algorithm — statement?

Unique $q, r$ with $a = dq + r$, $0 \\leq r < d$.

Divisibility — relation?

Exists $k$ with $b = ak$.

Linear combination — form?

$ax + by$, with integers $x, y$.

Quotients and Remainders — result?

From division: $a = bq + r$, with $0 \\leq r < b$.

Modular arithmetic — relation?

$a \\equiv b \\ ( ext{mod } m)$ if $m$ divides $a - b$.

Prime number — definition?

Divisible only by 1 and itself.

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Frequently asked questions

What does the Number Theory Fundamentals study guide cover?

It covers the core concepts of Number Theory Fundamentals, organized by topic with the key definitions, explanations and takeaways, so it's easier to learn and remember.

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How many questions are in the Number Theory Fundamentals quiz?

The practice quiz has 10 multiple-choice questions, each with an explanation. Use it to check what you know and find your gaps.

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There are 20 flashcards on Number Theory Fundamentals, with a question on the front and the answer on the back. Try to recall each answer before you flip, and let spaced repetition bring back the ones you miss.

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