Math Is Fun Forum

Jono

Guest

Matrices! Please help!

Solve the matrix equation AB= (3 9) for B when A = (1 1)
                                              0  0                          0 0

Im totally stuck on these so if anyone could help with a wee mini step by step guide to doing them it would be much appreciated

soroban

Member

Registered: 2007-03-09

Posts: 452

Re: Matrices! Please help!

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Jono

Guest

Re: Matrices! Please help!

Ok thank you!

Can I just ask why it is a+c and b+d in the top row of the second bit but not the same for the bottom bit? And why is that way?! Cant get my head round these at all

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Matrices! Please help!

Hi Jono;

Have you learnt matrix multiplication yet? There are rules for multiplying 2 matrices.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Jono

Guest

Re: Matrices! Please help!

Erm, we went over them quickly but Im struggling to understand how you multiply them. The rules seem to keep changing

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Matrices! Please help!

Hi Jono;

The rules seem to keep changing

Now you know rules never change! Here are some cute pages that will do a better job than I can do.

http://www.mathsisfun.com/algebra/matri … lying.html

uhttp://people.hofstra.edu/stefan_waner/ … es3_2.html

Please look at them. If you still can not get it I will go over a problem from one of those sites with you. But please look at those pages first, those people know how to explain it.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.