Proving Series Equations: A General Method

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SUMMARY

The discussion centers on proving the series equation for the sum of squares, specifically the formula \(1^{2}+2^{2}+\ldots+n^{2}=\frac{n(n+1)(2n+1)}{6}\). The approach involves solving the difference equation \(S(n)-S(n-1)=n^2\) with the initial condition \(S(1)=1\), leading to a third-order polynomial solution. In contrast, the series \(1^{1}+2^{2}+\ldots+n^{n}\) presents a challenge as its difference \(n^n\) does not yield a known simple function of \(n\).

PREREQUISITES
  • Understanding of difference equations
  • Familiarity with polynomial functions
  • Basic knowledge of series and summation formulas
  • Experience with mathematical proofs (excluding induction)
NEXT STEPS
  • Study the methods for solving difference equations
  • Explore polynomial interpolation techniques
  • Research advanced series summation techniques
  • Investigate the properties of exponential functions in series
USEFUL FOR

Mathematicians, educators, and students interested in series equations and mathematical proofs, particularly those looking to deepen their understanding of polynomial and difference equation methodologies.

glebovg
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How to prove (not by induction)

1^{2}+2^{2}+\ldots+n^{2}=\frac{n(n+1)(2n+1)}{6}?

What is the general approach for similar series, say, 1^{1}+2^{2}+\ldots+n^{n}?
 
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glebovg said:
How to prove (not by induction)

1^{2}+2^{2}+\ldots+n^{2}=\frac{n(n+1)(2n+1)}{6}?

What is the general approach for similar series, say, 1^{1}+2^{2}+\ldots+n^{n}?

For your first question, the sum is the solution to the difference equation S(n)-S(n-1)=n^2 subject to the initial condition S(1)=1. Since the difference is 2nd order polynomial, the solution is 3rd order polynomial, now you know how to proceed. For your second question, since the difference is n^n, no known simple function of n has such difference, therefore no simple solution.
 

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