Math Is Fun Forum

rcwitt

Member

Registered: 2010-12-09

Posts: 36

Quick Question About Matrices

I am new to matrices (and just about everything else), so be gentle. LOL

Can the following problems be solved?

And the second one (multiplication):

Bob

Administrator

Registered: 2010-06-20

Posts: 10,624

Re: Quick Question About Matrices

hi rcwitt

To add or subtract matrices, they must be the same 'shape';  ie. same number of rows and same number of columns.

So the two you give in your post cannot be added.  (first is 3 by 2; second is 2 by 3)

To multiply the number of columns in the first matrix must be the same as the number of rows in the second.

So if first is m by n  and the second is p by q then they may only be multiplied if n = p.

And, because of the way matrix multiplication works, the answer is m by q.

Your example ( 2 by 2 and 2 by 3 ) is possible with the result 2 by 3.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Bob

Administrator

Registered: 2010-06-20

Posts: 10,624

Re: Quick Question About Matrices

and division is not defined, but, if a matrix has an inverse, then you can 'divide'  A/B by doing A x (inverse of B)

B

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob