Are the following properties true? Linear Algebra

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Homework Help Overview

The discussion revolves around properties of matrices in linear algebra, specifically concerning the rank of a matrix and its transpose, as well as the dimensions of their null spaces.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore whether the statements regarding rank and null space dimensions are true or false, with some questioning the implications of matrix dimensions, particularly in the context of a 2 by 3 matrix.

Discussion Status

There is ongoing confusion about the properties being discussed, with participants expressing differing opinions on the truth of the statements. Some have suggested that the rank of a matrix and its transpose may be equal, while others are uncertain and seek clarification on related concepts such as row and column rank.

Contextual Notes

Some participants indicate a lack of familiarity with certain concepts, such as row space and the rank-nullity theorem, which may affect their understanding of the discussion.

flyingpig
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Homework Statement



Let A be a matrix

Then the following is true or false. (No need to explain why)

a) rank(A) = rank(At)
b) dim(Nul(A)) = dim(Nul(At)



The Attempt at a Solution



They are both true false right? The transpose swaps their row and columns which makes them interchanged

rank(A) = dim(Nul(At)

rank(At) = dim(Nul(A))
 
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flyingpig said:
They are both true false right?

Greetings! I'm somewhat confused. Consider a 2 by 3 matrix; is rank(A) = rank(AT)?
 
I meant to say "They are both false" right?
 
Undoubtedly0 said:
Greetings! I'm somewhat confused. Consider a 2 by 3 matrix; is rank(A) = rank(AT)?

Row rank does equal column rank, doesn't it? Isn't this fairly well known?
 
I have not learned RowSpace yet sorry, we cover that next term
 
flyingpig said:
I have not learned RowSpace yet sorry, we cover that next term

Then you maybe haven't done the rank-nullity theorem either. Maybe you should save this question for next term?
 
Dick said:
Row rank does equal column rank, doesn't it? Isn't this fairly well known?

Right right. I guess the point is that the rank of a matrix is simply the number of linearly independent columns (any 3x2 and any 2x3 matrix can both have at most 2 linearly independent columns). Does this help at all flyingpig?
 

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