Linear Algebra and Determinant

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Discussion Overview

The discussion revolves around constructing specific 4x4 matrices that exhibit distinct properties regarding the ease of computing their determinants using cofactor expansion versus elementary row operations. The focus is on theoretical aspects of linear algebra and determinant evaluation techniques.

Discussion Character

  • Exploratory
  • Mathematical reasoning

Main Points Raised

  • Some participants propose a diagonal matrix with random elements from the uniform distribution U(0,1) as a candidate for easy determinant computation via cofactor expansion.
  • Others suggest a matrix with two equal rows, also with elements sampled from U(0,1), as a case where elementary row operations would easily show a zero determinant, but cofactor expansion might be more complex.
  • Several participants seek clarification on the notation U(0,1), indicating a lack of understanding of the uniform distribution concept.
  • A participant explains that U(0,1) refers to the uniform distribution on the interval [0,1), relating it to the proposed matrix constructions.

Areas of Agreement / Disagreement

Participants generally agree on the types of matrices that could be constructed for the problem, but there is some uncertainty regarding the understanding of the uniform distribution and its implications for the matrix properties.

Contextual Notes

Some assumptions about the properties of determinants and the implications of matrix row operations may not be fully articulated, leading to potential misunderstandings in the discussion.

Swati
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1(a) Construct a 4*4 matrix whose determinant is easy to compute using cofactor expansion but hard to evaluate using elementary row operations.

(b) Construct a 4*4 matrix whose determinant is easy to compute using elementary row operations but hard to evaluate using cofactor expansion
 
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Swati said:
1(a) Construct a 4*4 matrix whose determinant is easy to compute using cofactor expansion but hard to evaluate using elementary row operations.

Would a matrix with all elements zero except for those on the diagonal which are a random sample of size 4 from U(0,1) qualify?

(b) Construct a 4*4 matrix whose determinant is easy to compute using elementary row operations but hard to evaluate using cofactor expansion

Would a matrix with two rows equal but with values samples from U(0,1), and all other values sampled independently from U(0,1) qualify?

CB
 
what is U(0,1) ?
Please explain me, i couldn't understand.
 
Swati said:
what is U(0,1) ?
Please explain me, i couldn't understand.

U(0,1) - the uniform distribution on [0,1). The suggestion is to use a random matrix generated in the specified way. In one case it would be diagonal, so the co-factor method would give the determinant as the product of the diagonal elements, in the second case with two equal rows row operations would deduce it has zero determinant.

CB
 

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