# Matrix operations

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Samantha Steele on 20 Sep 2011
So i am having trouble with one of my homework problems..
i am given matrices
A=[1,21,3;5,7,9;11,12,32];
B=[2,3,4;5,8,11;8,9,22];
C=[2,3,4;7,9,11];
and need to perform the following operations:
inv(A)
A*inv(A)
A*A'
A.*B
A.*C %need help here%
%multiplication%
A=[1,21,3;5,7,9;11,12,32];
B=[2,3,4;5,8,11;8,9,22];
C=[2,3,4;7,9,11];
A*B;
B*A;
A*C;%and here%
C*A%and here%
but for the marked locations matlab gives me an error message.. what can i do differently?
the cyclist on 21 Sep 2011
It would be really helpful if you could use the "code" button to format your question. It's really difficult to read.

bym on 21 Sep 2011
A is size 3x3, C is size 2x3, therefore:
A.*C
A*C
C*A
are all errors because of dimensions. Without further information you can't do anything differently. Perhaps that was the goal of the assignment?
##### 2 CommentsShowHide 1 older comment
Walter Roberson on 21 Sep 2011
>> A=[1,21,3;5,7,9;11,12,32];
>> C=[2,3,4;7,9,11];
>> C*A
ans =
61 111 161
173 342 454
Doesn't look like an error to me...

Walter Roberson on 21 Sep 2011
I would expect errors for A.*C and A*C, but I would not expect an error for C*A: I would expect a 2 x 3 matrix as the result.