Problem with matrix echelon form

asked 2023-09-07 07:03:34 +0200

Sotto
31 ●1

updated 2023-09-07 09:09:15 +0200

FrédéricC

5123 ●3 ●43 ●111

Dear all,

if we define A to be

A = matrix([[1,-3,0,2],[-2,4,0,h],[0,-2,1,k],[3,-1,7,1]])
A.echelon_form()

gives diag(1,1,1,1). But this is wrong for some values of h and k.In some cases the last 1 could be 0.

How can I fix this? Thanks, N

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Comments

A possible approach would be defining a function of h and k.

Max Alekseyev ( 2023-09-07 17:29:37 +0200 )edit

Sorry not clear enough for me … What do you mean?

Sotto ( 2023-09-09 12:27:11 +0200 )edit

Like this:

def myform(h,k):
    A = matrix([[1,-3,0,2],[-2,4,0,h],[0,-2,1,k],[3,-1,7,1]])
    return A.echelon_form()

Max Alekseyev ( 2023-09-09 14:46:49 +0200 )edit

I see. Thanks. But in this case I have to enter the values for h and k. That's not what I want... I'd like Sage to tell me what condition on h and k gives an echelon form like drag(1,1,1,1) and which one gives drag(1,1,1,0).

Sotto ( 2023-09-10 10:13:37 +0200 )edit

diag not drag :-)

Sotto ( 2023-09-10 10:15:11 +0200 )edit

add a comment

[ 1 0 0 -3/2*h - 4] [ 0 1 0 -1/2*h - 2] [ 0 0 1 -h + k - 4] [ 0 0 0 11*h - 7*k + 39]

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