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How do you verify a statement like a≡b(modn)a \equiv b \pmod{n} in this video?

To verify a≡b(modn)a \equiv b \pmod{n}, divide aa by the modulus nn using long division and check if the remainder is bb. If the remainder matches bb, the congruence is valid.

Conditions

  • The method is demonstrated for positive dividends and positive moduli.
  • The speaker calls it a colloquial explanation.

Reasoning, step by step

  1. Identify the dividend aa and the modulus nn.
  2. Perform long division of aa by nn.
  3. Find the remainder of the division.
  4. Compare the remainder with bb.
  5. Conclude validity if they match.

Example

For 15≡3(mod12)15 \equiv 3 \pmod{12}, the video shows long division: 15 divided by 12 gives quotient 1 and remainder 3. Since the remainder is 3, the congruence is valid.

Common misconceptions

  • Assuming the quotient matters for the congruence (only the remainder is compared).
  • Thinking the remainder must always be the least nonnegative residue (the video later accepts 14 as a remainder for 38 mod 12, though 2 is the standard).

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Answers are generated from source material and independently checked. Consult the original video or creator if something is unclear.