Question

can some one please help me? i will medal AND fan!!:)

Answer 1

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

Answer 2

how did you get that?

Answer 3

just take inverse of C

Answer 4

thats the inverse of c? could u show me how you got that?

Answer 5

let me call expert. @ganeshie8

Answer 6

C^- = 1/detC *{adjoint C}, you should know it, right?

Answer 7

oh ok.. but what do we do next?

Answer 8

I don't know, hihihi, just support you to find C^-

Answer 9

@Loser66 how do we use C-1 to decode the other matrix?

Answer 10

@phi ?

Answer 11

@AccessDenied ?

Answer 12

the code is Great work

Answer 13

if we call the phrase E (for encoded) and M the original (for message)
they did
CM = E
(multiplied C times matrix M to get the encoded matrix)

Answer 14

\(C^-\)* the next matrix to get the new matrix, and then apply the table to get the word

Answer 15

so we divide them?

Answer 16

\[ C M = E \\ C^{-1} C M = C^{-1}E \\ M= C^{-1}E \]

Answer 17

do you know how to multiply matrices ?

Answer 18

yep :)

Answer 19

wait, does C stand for the original C , or the C-1?

Answer 20

C is code, C^- is encode

Answer 21

C is the original and \( C^{-1} \) is the inverse. Use the inverse

Answer 22

they even tell you "find C inverse and use it..."

btw, to find the inverse of a 2 x 2 see
http://www.mathsisfun.com/algebra/matrix-inverse.html
and scroll down to the 2x2 example

Answer 23

so use C-1 as the C in the equation?

Answer 24

you will do this
\[ M= C^{-1}E \]
where C inverse is what Loser66 posted up above and E is the coded matrix

Answer 25

And M represents the original C right?

Answer 26

M will be 2 x 6 matrix of the message (that you will be able to read)

Answer 27

ooh ok so for now, i just multiply c^-1 with E?

Answer 28

yes. C^-1 goes in front of E (order matters)

Answer 29

oh ok! i will do that, and then can i have you check it when im done?:)

Answer 30

yes. But if you get the correct answer it will be obvious. if the message looks something like
RQUTAP
IUUYWX
it is wrong!

Answer 31

lol oh yeah.. :) nvm then:) i'll just mention you if i get stuck:) thanks so much!!:)