Prove that Col(A) is a proper subset of Nul(A)

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Homework Help Overview

The discussion revolves around proving that for a given nxn matrix A, where A^2=0, the column space of A (Col(A)) is a proper subset of the null space of A (Nul(A)). Participants express confusion regarding the definitions and implications of the terms involved in the problem.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Some participants question the meaning of the problem and seek clarification on the relationship between Col(A) and Nul(A). Others express uncertainty about how to approach the proof and whether specific assumptions about the matrix A, such as it being non-zero, are necessary.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem. Some guidance has been offered regarding the need to prove the existence of elements in Nul(A) that are not in Col(A), but there is no consensus on the assumptions or the approach to take.

Contextual Notes

Participants note that the problem may require clarification on whether A is a non-zero matrix, which could affect the proof. There is also some confusion about the terminology used, particularly regarding the terms "kernel" and "column space."

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Homework Statement



Prove that if A is a nxn matrix such that A^2=0, then Col(A) is a proper subset of Nul(A)


Homework Equations





The Attempt at a Solution



None, i have no idea how to start.
Please guide me or explain what does the question means and how to approach.
 
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hi junsugal! :smile:

(do you mean Ker(A)? it's spelled "kernel", not "colonel" … a kernel is the soft part inside the shell of a nut! :biggrin:)

it means you have to prove that there exists an x such that x is in Nul(A) but not Col(A)

(i think the question should have stipulated that A is non-zero)
 
tiny-tim said:
hi junsugal! :smile:

(do you mean Ker(A)? it's spelled "kernel", not "colonel" … a kernel is the soft part inside the shell of a nut! :biggrin:)

it means you have to prove that there exists an x such that x is in Nul(A) but not Col(A)

(i think the question should have stipulated that A is non-zero)


Hi :)

It is Col(A).
I thought it means that Nul(A) is a subspace of Col(A)?
well, I'm still confused though.
I tried to solve this problem asuming that A is zero matrix.
Because I couldn't think of any nxn matrix that will get zero after multiply by itself.
 
junsugal said:
I thought it means that Nul(A) is a subspace of Col(A)?

no …
junsugal said:
… Col(A) is a proper subset of Nul(A)

… means that Col is a subset of Nul, but is less than Nul
I tried to solve this problem asuming that A is zero matrix.

no!

A must be non-zero
 

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