Division of integer square by 4 leaves remainder 0 or 1

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Discussion Overview

The discussion centers on the properties of integer squares when divided by 4, specifically exploring why the remainder is always 0 or 1. The scope includes mathematical reasoning and conceptual clarification.

Discussion Character

  • Mathematical reasoning

Main Points Raised

  • One participant proposes that integers can be categorized as even or odd, leading to different behaviors when squared.
  • In the case of even integers (n=2x), it is suggested that their squares yield a remainder of 0 when divided by 4.
  • For odd integers (n=2x+1), it is claimed that their squares yield a remainder of 1 when divided by 4.
  • Another participant reiterates that every odd integer squared has a remainder of 1, while every even integer squared is a multiple of 4.
  • Participants provide algebraic expressions to support their claims regarding the behavior of even and odd integers when squared.

Areas of Agreement / Disagreement

Participants generally agree on the classification of integer squares yielding remainders of 0 or 1 when divided by 4, but the discussion does not explore any competing views or unresolved questions.

Contextual Notes

None noted.

Who May Find This Useful

Readers interested in number theory, modular arithmetic, or properties of integers may find this discussion relevant.

bluemoon2188
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Hi,

I am looking for an explanation, if any, on why every integer square leaves remainder 0 or 1 on division by 4.

Appreciate your time and help

bluemoon2188
 
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I guess we should divide the integers into (1) even numbers (2) odd number.

Case 1:
n=2x
Then
n^2\equiv4x^2\equiv0 \mbox{ mod } 4

Case 2:
n=2x+1
Then
n^2\equiv4x^2+4x+1\equiv4(x^2+x)+1\equiv1 \mbox{ mod } 4

So in general, any even number squared equals 0 mod 4 and every odd number squared equals 1 mod 4. Hope that helps!
 
Actually, you can say more. Every odd integer, squared, has remainder 1 when divided by 4, every even integer, squared, is a multiple of 4.

Every integer is either even or odd. That is every integer is equal to 2n, for some integer n, or 2n+1 for some integer n.

(2n)2= 4n2

(2n+ 1)2= 4n2+ 4n+ 1

Two minutes too slow!
 
hey guys,

Thanks for the help. Didn't see that coming.

Cheers
 

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