Determinant of symmetric matrix with non negative integer element

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Discussion Overview

The discussion revolves around the determinant of a specific symmetric matrix with non-negative integer elements, represented as matrix A. Participants explore methods to prove a proposed formula for the determinant, including specific cases and general proof strategies.

Discussion Character

  • Exploratory, Technical explanation, Homework-related

Main Points Raised

  • One participant presents the matrix A and asks for a proof of the determinant formula det(A) = [(-1)^n][n][2^(n-1)].
  • Another participant suggests testing the case where n=4 to explore the determinant's value.
  • A different participant proposes using mathematical induction to establish a general proof, indicating that the transition from n=k to n=k+1 involves evaluating an additional minor determinant.
  • Another suggestion is made to simplify the matrix by adding or subtracting rows or columns to facilitate the calculation of the determinant.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the proof method or the determinant's value for n=4, as various approaches are suggested without agreement on a single solution.

Contextual Notes

The discussion includes various assumptions about the properties of determinants and matrix operations, but these assumptions are not explicitly stated or resolved.

Who May Find This Useful

Readers interested in linear algebra, particularly in the properties of determinants and symmetric matrices, may find this discussion relevant.

golekjwb
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Let \begin{equation*}
A=%
\begin{bmatrix}
0 & 1 & \cdots & n-1 & n \\
1 & 0 & \cdots & n-2 & n-1 \\
\vdots & \vdots & \ddots & \vdots & \vdots \\
n-1 & n-2 & \cdots & 0 & 1 \\
n& n-2 & \cdots & 1 & 0%
\end{bmatrix}%
\end{equation*}.
How can you prove that det(A)=[(-1)^n][n][2^(n-1)]? Thanks.
 
Last edited:
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Try n=4
 
golekjwb said:
Try n=4

Hey golekjwb and welcome to the forums.

For the general proof I would use an induction argument. The differences between say n = k and n = k + 1 has to do with evaluating one extra minor determinant for that extra row and you would show that under a simplification that the formula is correct.

For a specific n=4, just evaluate the determinant for that particular dimension for your particular matrix, expand out and see what you get.
 
welcome to pf!

hi golekjwb! welcome to pf! :smile:

have you tried adding or subtracting rows or columns, to get a simpler matrix?
 

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