Question

@rational I need to know I'm understanding this correctly.

Answer 1

It says the matrix C was used to encode a certain matrix. It says to find C^(-1), which I know is the the inverse.. and use it to decode the matrix. I'm not sure if I'm supposed to encode the matrix, with C and then multiply the encoded matrix my C^(-1).. do you understand what I'm asking?

Answer 2

suppose you have \(x \) and multiplied this by a matrix \(C\) producing \(y\) :

\[\large Cx = y\]

To get back \(x\), you can simply find the inverse of \(C\) and multiply it by \(y\) :
\[x = C^{-1}y\]

Answer 3

hey post the actual question if above looks confusing

Answer 4

so is what I said to do correct?

Answer 5

no, it looks fine.

Answer 6

wouldn't x be the same?

Answer 7

yes what you said looks good to me :)

Answer 8

so I have \[C=\left[\begin{matrix}1 & -2 \\ -3 &7\end{matrix}\right]\] and the other matrix is \(\begin{matrix}7&-28&-25&-35&-2\\-21&107&90&123&17\end{matrix}\)

Answer 9

so I multiply those, then take the inverse of C and and divide the inverse by the product?

Answer 10

that other matrix is the encoded matrix ?

Answer 11

it doesn't specify if it's the encoded one or not.

Answer 12

can you take a screenshot and post the full q

Answer 13

good the second long matrix is ENCODED matrix,
we need to decode it by finding the inverse of C

Answer 14

start by finding the inverse of C

Answer 15

how can you tell it's encoded?

Answer 16

because the question says so !

Answer 17

It does?

Answer 18

yes read it 2-3 times and convince urself first :)

Answer 19

anyways, \[C^{-1}=\left[\begin{matrix}7 & 2 \\ 3 & 1\end{matrix}\right]\] right?

Answer 20

Yes!

Answer 21

use that decode the given matrix

Answer 22

do I multiply it by the encoded matrix?

Answer 23

\[\begin{bmatrix} 7&2\\3&1\end{bmatrix}\begin{bmatrix}7&-28&-25&-35&-2\\-21&107&90&123&17\end{bmatrix}\]

Answer 24

Okay, I guess I was right! one moment, let me multiply this out.

Answer 25

okay good luck! you need to work one column at a time, 5 times.

Answer 26

I know XD

Answer 27

you seem to be knowing matrices better than me :)

Answer 28

I've done them before, I moved to a new school, and they're just now teaching them... but I learned in the first semester, so I'm a little rusty XD

Answer 29

\(\begin{matrix}7&18&5&1&20\\0&23&15&18&11\end{matrix}\)

Answer 30

@rational

Answer 31

@rational

Answer 32

@rational is it right?

Answer 33

I checked first two columns, they are correct! i wouldn't doubt you made mistakes with other columns

good job :)

Answer 34

thank you XD

Answer 35

yw:)