Just some basic matrices

[monkeywantsabanana]

Hey guys this is odd - check it out...

W= [2 -3]
      [4  6]

and V = [4  0]
            [3 -1]

find X such that WX=V...

so..


X = W^-1 times V
if i type that into calculator i get the right answer
but if i do it by hand i get a different answer - by hand my next step would be

det W = 24
W^-1 = 1/24 [6  3]   [4  0]
                   [-4 2]   [3 -1]

i type that into calculator I get a different answer, does anyone know why this is?

Sorry guys, idk how to do the math working out on the forum - it looks messy.

All replies appreciated.

[luffy]

This is my working (by hand) - Sorry if I made any errors:

















Hope I helped.

[monkeywantsabanana]

I got that too!!

but - when you do that times by W you don't get V

Why is this ?

[BubbleWrapMan]

It's different if you multiply it as WV or VW, maybe that's it?

[iNerd]

It's different if you multiply it as WV or VW, maybe that's it?

This. With matrices you multiply by order.

[monkeywantsabanana]

Ah that's right.
Silly me...

THANK YOU ALL !!!

can some one teach me how to do the working out that 'luffy' did?

[pi]

Do you mean or the actual mathematical process?

[monkeywantsabanana]

not the process. how to do the process with that font. :O

[pi]

not the process. how to do the process with that font. :O

Its a long explanation

Firstly, you can use it through the 'TEX' button (when you hit 'reply', the button is under the 'change colour' dropdown box).

Then, try and experiment with some simple things here.

Some stuff not on there:
To create a matrix:

Code: [Select]

[tex] A = \begin{bmatrix}
w & x \\
y & z
\end{bmatrix} [/tex]

For fractions:

Code: [Select]

[tex]A = \frac{x}{y}[/tex]

I'm still learning too! 

[monkeywantsabanana]

thanks !