Thread: Matrix and vector multiplication

Dear NotGoodAtMath94,

Your multiplication of matrices is incorrect. The correct one is,

* =

Hope this will help you.

Thank you for showing me

Originally Posted by NotGoodAtMath94

Hello,
Im trying to learn the rules for multiplying a row vector and matrix together, can anyone please tell me if Im right or wrong about:


* =

Think of a matrix multiplication as a series of "dot products". The number at the "i,j" place in the product AB is the dot product of the ith row of A and the jth column of B.

In your example, row 1 of A is (a, b, c) and column 1 of B is (e, h, k). The "dot product" of those is ae+ bh+ ck so your first number in the first column is ae+ by+ ck, not ae+ ah+ ak where you have multiplied the first column by a only.

In this case, since A has only one row, the product has only one row.

Hello, NotGoodAtMath94!

We multiply the row vector by each column vector.


The three multiplications are:

. .

. .

. .


Since , the product is a row vector:

. . . .