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#1 2013-05-28 04:37:39

mom
Member
Registered: 2012-04-25
Posts: 94

Just want to make sure I am doing this correctly

I have:
Let A=[-2 1 3] and B = [0 1 -3]. Find the second row of AB.
            1 0 5                1 3 -4
            0 4 2                3 0  1

I multiplied and for the second row of AB, I got [15 1 2]

Is this correct?

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#2 2013-05-28 05:07:24

{7/3}
Member
Registered: 2013-02-11
Posts: 210

Re: Just want to make sure I am doing this correctly

I'm confused,how can 1 by 3 and 1 by 3 matrices be multiplied?


There are 10 kinds of people in the world,people who understand binary and people who don't.

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#3 2013-05-28 05:24:35

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,121

Re: Just want to make sure I am doing this correctly

hi mom,

That's correct.

{7/3} :  I think those are two 3 x 3 matrices.

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#4 2013-05-28 05:26:34

mom
Member
Registered: 2012-04-25
Posts: 94

Re: Just want to make sure I am doing this correctly

Please see attached. I have never uploaded in here before but the attachment shows how I did my work.

I know how to go through the process of multiplication for the matrices. I am just not sure that is what the question was asking me to do.

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#5 2013-05-28 05:31:03

mom
Member
Registered: 2012-04-25
Posts: 94

Re: Just want to make sure I am doing this correctly

Bob,

yes they are two 3 x 3 matrices. So for the second row of AB it would be [15 1 2] ?

It didn't say to multiply so I wasn't sure that I worked the problem correctly but if you have A matrix B matrix and you have to come up with the second row of AB for the matrices, was I correct in assuming that I was to multiply?

Thanks so much.

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#6 2013-05-28 05:32:12

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,121

Re: Just want to make sure I am doing this correctly

Yes; in matrix work AB means A multiplied by B.

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#7 2013-05-28 05:46:15

mom
Member
Registered: 2012-04-25
Posts: 94

Re: Just want to make sure I am doing this correctly

Bob,

thanks so much.

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