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# Matrices watch

1. Vgbg
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2. In order for a Matrix multiplication to be allowed... the number of columns in the first matrix must be equal to the number of rows in the second matrix.
3. AxB
BxC
CxA
CxB

just set out the matrices as 2x2 for A, 2x3 for B, 3x2 for C.
then put them next to each other e.g. AB (2x2 2x3), the middle numbers are both 2 so it means it would work.
another one for example is BC (2x3 3x2) both middle numbers are 3.
Try it for CxA and CxB
4. (Original post by Deeboss)

Q15

Could some please explain this to me. I am having a hard time learning matrices. How am I mean to work this out?
Matrices are kewl.

It would help to write down the dimensions of each matrix; number of rows, by number of columns.
B would be (2x3)

AB - To multiply matrices together, the number of columns of Matrix A needs to be equal to the number of rows of matrix B

This also determines the dimensions of matrix AB. Number of rows of matrix A, number of columns of matrix B

If you need anything else.
I don't even talk to the guy but RDKGames is a lad. Always happy to help.
5. (Original post by robinhood111)
AxB
BxC
CxA
CxB
M8 ur sik @ explaining tings.
6. hope it helps, thats the easiest way i could think of
7. (Original post by Maths is Life)
Matrices are kewl.

It would help to write down the dimensions of each matrix; number of rows, by number of columns.
B would be (2x3)

AB - To multiply matrices together, the number of columns of Matrix A needs to be equal to the number of rows of matrix B

This also determines the dimensions of matrix AB. Number of rows of matrix A, number of columns of matrix B

If you need anything else.
I don't even talk to the guy but RDKGames is a lad. Always happy to help.
Why would the answer not be AxC or BxA?
8. (Original post by Deeboss)

Q15

Could some please explain this to me. I am having a hard time learning matrices. How am I mean to work this out?
For an arbitrary matrix of size where the number of rows is denoted by and the number of columns denoted by , the product of two matrices, , is only valid when

So you can denote matrix sizes:

then see for which product combinations of two matrices the rule holds.

If you want to see why it is so, simply attempt to multiply out an option which is against the rule.

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