Quick matrix question.

For the discussion of math. Duh.

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Hasbren
Posts: 31
Joined: Tue Apr 14, 2009 4:07 pm UTC

Quick matrix question.

Postby Hasbren » Sat Jan 30, 2010 10:20 pm UTC

If I have 4X2 matrix like this
[ 2 5 ]
[ 1 3 ]
[ 0 5 ]
[ 2 2 ]

Shouldn't the rref be
[ 1 0 ]
[ 0 1 ]
[ 0 0 ]
[ 0 0 ]

Anyway, my calculator hated me for it- and I was wondering if xkcd would know the answer.

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NathanielJ
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Re: Quick matrix question.

Postby NathanielJ » Sat Jan 30, 2010 10:33 pm UTC

Hasbren wrote:Shouldn't the rref be
[ 1 0 ]
[ 0 1 ]
[ 0 0 ]
[ 0 0 ]


Yes.
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Hasbren
Posts: 31
Joined: Tue Apr 14, 2009 4:07 pm UTC

Re: Quick matrix question.

Postby Hasbren » Sat Jan 30, 2010 11:13 pm UTC

Just found out that it's a problem with the TI calculators. Quick fix is to make the matrix a 4X4 with extra zero columns.

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Talith
Proved the Goldbach Conjecture
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Re: Quick matrix question.

Postby Talith » Sun Jan 31, 2010 1:57 am UTC

You seriously used a calculator to work this out? Christ some people are lazy....

[Edit]I didn't mean to sound nasty, but you have to admit, using a calculator to work this out is overkill to the extreme. Sorry if it came across as a flame.[/Edit]
Last edited by Talith on Mon Feb 01, 2010 12:28 am UTC, edited 1 time in total.

Hasbren
Posts: 31
Joined: Tue Apr 14, 2009 4:07 pm UTC

Re: Quick matrix question.

Postby Hasbren » Sun Jan 31, 2010 7:41 pm UTC

lol-- easy dude! The math professor told us to try it both ways. I was just confused as to why it didn't work.

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Dason
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Re: Quick matrix question.

Postby Dason » Sun Jan 31, 2010 8:10 pm UTC

Talith wrote:You seriously used a calculator to work this out? Christ some people are lazy....


Just saying... I didn't really see a need for your post. I'm not a mod but...

gmalivuk wrote:Rule the third:
Keep things civil. Sticks on the ice boys and girls. If you don't agree with someone on a particular theory/question do not attack them. [snip] Flames will definitely be deleted, as it's easier to delete a post than edit out the flameness. Don't run the risk of a perfectly good argument being deleted because you wanted to make someone feel like an idiot.


I'm sure you're familiar with the rules
double epsilon = -.0000001;

achan1058
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Re: Quick matrix question.

Postby achan1058 » Sun Jan 31, 2010 9:33 pm UTC

Row 3 and 4 forms an invertible submatrix, so there's actually no need to work anything out.

DavCrav
Posts: 251
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Location: Oxford, UK

Re: Quick matrix question.

Postby DavCrav » Sun Jan 31, 2010 11:33 pm UTC

achan1058 wrote:Row 3 and 4 forms an invertible submatrix, so there's actually no need to work anything out.


Any two rows form an invertible submatrix...


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