Can a Singular Matrix Always Find a Partner Matrix to Result in Zero?

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SUMMARY

A singular matrix A will always have a corresponding non-zero matrix B such that the product AB (or BA) results in the zero matrix. This is due to the existence of a non-zero column vector x for which Ax=0, allowing B to be constructed from the null space of A. Specifically, any matrix formed by selecting columns from the null space will satisfy the condition for B. Additionally, the columns of matrix A span its column space, further confirming this relationship.

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ohyeahstar
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Just a small question, I think I may have missed this part out in our lectures or something. :|

Suppose I have a singular matrix A; will there always exist another matrix B such that AB (/BA) will be the zero matrix?
 
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Yes, take B the zero matrix :smile: but you mean non-zero matrices, I suppose.

Well, if A is singular, then there always exists a nonzero column vector x such that Ax=0. Then B=(x x ... x) should do the trick.
 
Welcome to PF ohyeahstar! :smile:

Yep, as mm said!

More specifically, a matrix has a so called "null space" (or "kernel space") and a so called "column space" (or "image" or "range" of the matrix).
Any matrix with columns selected from the null space will satisfy your criterion for B.
Furthermore the columns from your matrix A "span" the column space.
 

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