Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

I wanted to make the title: 'When is Matrix Multiplication Well-Defined', but the software wouldn't let me.

If we have two matrices $A$ and $B$, then $AB$ is well defined if and only if the number of columns of $A$ equals the number of rows of $B$.

Is this right?

share|improve this question
1  
Yes, that’s exactly right. –  Brian M. Scott Dec 8 '12 at 23:10
    
Great, thanks a lot! –  matrix Dec 8 '12 at 23:12
    
My pleasure. $\,$ –  Brian M. Scott Dec 8 '12 at 23:13

1 Answer 1

If $A=(a_{ij})$ and $B=(b_{jk})$ are matrices, with $1\leq i\leq n$, $1\leq j\leq p$, $1\leq k\leq q$ then the product $C=AB=(c_{ik})$ is the $(n\times q)$-matrix define by $c_{ik}=\sum_{j=1}^{p}a_{ij}b_{jk}$.

Here is an image from TeXample.net TeXample.net

share|improve this answer
1  
Nice picture! You should share it on Wikipedia ;) –  Damian Sobota Dec 8 '12 at 23:29

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.