Number Theory Division Algorithm interesting problem

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SUMMARY

The discussion centers on proving that any integer raised to the fourth power can be expressed as either 5k or 5k+1, where k is an integer. Participants suggest starting with the representation of integers in modulo 5 and computing the fourth power of each residue class. The conversation also touches on the potential use of proof by induction as a method for establishing the claim. Key insights include the importance of understanding arithmetic modulo 5 and the implications of expanding binomials.

PREREQUISITES
  • Understanding of modular arithmetic, specifically modulo 5
  • Familiarity with binomial expansion
  • Knowledge of proof techniques, particularly proof by induction
  • Basic concepts of number theory
NEXT STEPS
  • Research modular arithmetic and its applications in number theory
  • Study binomial expansion and its relevance in algebraic proofs
  • Learn about proof by induction and its use in mathematical arguments
  • Explore integer properties and their behavior under exponentiation
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Students of mathematics, particularly those studying number theory, educators looking for teaching strategies, and anyone interested in mathematical proofs and modular arithmetic.

PsychonautQQ
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Homework Statement


Not actually for homework, but i didn't know where to post this.

Problem: Show that any integer to the fourth power can be expressed as either 5k or 5k+1 where k is an integer.

Homework Equations


None.

The Attempt at a Solution


My starting point is to consider that all integers can be expressed as either:
2x or 2x+1

taking these to the fourth power I arrive at:
16k or 16k + 1

now I'm stuck, any tips? am i even on the right trail here?
 
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PsychonautQQ said:
My starting point is to consider that all integers can be expressed as either:
2x or 2x+1

You could start by considering they can be expressed as one of:
5x, 5x+1, 5x+2, 5x+3, 5x+4

If you are familiar with arithmetic modulo 5, you could compute the 4th power of each of the 5 residue classes.
 
2x4 = 16k I can understand.
But perhaps you want to reconsider (2x+1)4 = 16k+1. How did you do that ?

On another note: are you familiar with proof by induction ?
 

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