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 Post subject: Matrix multiplication problemPosted: Fri, 8 Oct 2010 22:45:25 UTC
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Joined: Mon, 19 Apr 2010 13:45:05 UTC
Posts: 61
Find all matrices X satisfying AX = XA, where A = .

=

I dont know what more to do

Last edited by TsAmE on Sat, 9 Oct 2010 14:53:19 UTC, edited 5 times in total.

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 Post subject: Posted: Fri, 8 Oct 2010 23:00:00 UTC
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Joined: Wed, 1 Oct 2003 04:45:43 UTC
Posts: 9633
Double check your work. The matrices weren't multiplied correctly.

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 Post subject: Posted: Sat, 9 Oct 2010 13:46:10 UTC
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Joined: Mon, 19 Apr 2010 13:45:05 UTC
Posts: 61
I forgot the equals sign for the last step. I have edited the post. Otherwise I check my multiplication and didnt see anything wrong.

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 Post subject: Posted: Sat, 9 Oct 2010 13:57:48 UTC
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Joined: Mon, 29 Dec 2008 17:49:32 UTC
Posts: 6009
Location: 127.0.0.1, ::1 (avatar courtesy of UDN)
TsAmE wrote:
I forgot the equals sign for the last step. I have edited the post. Otherwise I check my multiplication and didnt see anything wrong.

Are you sure you copied A correctly?

TsAmE wrote:
Find all matrices X satisfying AX = XA, where A = .

=

I dont know what more to do

_________________

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 Post subject: Posted: Sat, 9 Oct 2010 14:56:12 UTC
 Senior Member

Joined: Mon, 19 Apr 2010 13:45:05 UTC
Posts: 61
Sorry made a mistake A is suppose to = .

I found my mistake. Here is my correction:

Im not sure what to do from here.

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 Post subject: Posted: Sat, 9 Oct 2010 16:21:50 UTC

Joined: Sat, 26 Apr 2003 22:14:40 UTC
Posts: 2063
Location: El Paso TX (USA)
Two matrices are equal if their respective entries are equal. That gives you four equations...

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The greater danger for most of us lies not in setting our aim too high and falling short; but in setting our aim too low, and achieving our mark. - Michelangelo Buonarroti

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 Post subject: Posted: Sat, 9 Oct 2010 19:20:50 UTC
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Joined: Mon, 19 Apr 2010 13:45:05 UTC
Posts: 61
helmut wrote:
Two matrices are equal if their respective entries are equal. That gives you four equations...

I then get the equations:

x1 = x1 + 2y1
y1 = 0
2x1 = x2 + 2y2
2y1 = 0

From this info I found that:

y1 = 0
x1 = x1
Cant solve for x2

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 Post subject: Re: Matrix multiplication problemPosted: Sun, 10 Oct 2010 15:02:47 UTC
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Joined: Mon, 19 May 2003 19:55:19 UTC
Posts: 7950
Location: Lexington, MA
Hello, TsAmE!

Quote:
Find all matrices satisfying , where .

Let: .

Then we have: .

. . . . . . . . . . . . . . . .

Hence, we have four equations: .

From [3] and [4] we have: .

. . . . . Then [1] becomes: .

. . .And from [3] we have: .

Therefore: . . for any values of and

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