I need help with this simple matrix...?

Question

Multiply matrix D by matrix E

D = [ 5 -2 1] <-------- That is supposed to be vertical with the 5 on top, then the -2, then the 1.

E = [ 1 2] <--------- This one is hoizontal

I'm trying to help my younger brother with this...I mean calculus is a breeze, give me something to integrate and there's no problem, but to multiply matrices, I'm at a loss...It's been forever since I've done this...

Thanks

Answer 1

The first matrix is 3x1 and the second matrix is 1x2.
The resulting matrix will be 3x2.
[5]
[-2] [1 2]
[1]

=
[5 10]
[-2 -4]
[1 2]

Note: The above is all one matrix. I just used brackets for each row.

Here are the steps. For the entry in row 1 column 1, take row 1 of the first matrix and multiply it with the corresponding entries in column 1 of the second matrix.
(5)(1) = 1
For row 1 column 2, take row 1 of the first matrix and multiply it with the corresponding entries in column 2 of the second matrix.
(5)(2) = 10
And so on.

Answer 2

In general, multiply matrices row by column. The resulting element is found by multiplying corresponding elements and adding. The number of elements in the row must equal the number of elements in the column. In the example above, the dimensions of the matrices are incompatible and multiplication is not defined.

Answer 3

explaining matricies over the PC is a pain in the butt. check out some of your old algebra books for explanations and examples.

Or you can venture through some online websites to refresh your memory.

Answer 4

i cant remember but go to the site below. it is an on line Matrix calculator so you can always do it. Good luck.

Answer 5

here 2 factors (the intercepts of the line) on the plot of x2 as against x1, (0,a million) and (-2,0) grow to be (-a million,a million) and (-4,2), respectively and so its scaling and shearing the line inflicting it to "stretch". Former factors at the instant are added aside and the slope is far less steep between former factors.

Answer 6

it is not possible. (dim mismatch)