## anonymous one year ago The Matrix c=1 -2 (top)-3 7(bottom) was used to encode a phrase to [7 -28 -25-35-2 -21 107 90 123 17] . find C^_ and use it to decode the matrix. I need someone to show me how i would decode a matrix. i will become a fan and give a medal to whoever helps me

1. anonymous

2. anonymous

*the screenshots are easier to understand * I will BECOMe a Fan*

3. perl

you can encode it using column vectors

4. anonymous

i dont know what that is

5. perl

which one do you want help with, number 13?

6. anonymous

yes

7. perl

ok we want to encode the phrase, one question to go. i believe we want to include spaces. so we can use a matrix

8. anonymous

isn't 1 -2 the matrix ? -3 7

9. perl

The idea here is to code it this way $$\begin{bmatrix} 1 & -2 \\ -3& 7 \end{bmatrix} \cdot \begin{bmatrix} O & E& Q& E & T & O\\ N &\_ & U & S & I & N \end{bmatrix}$$

10. anonymous

so what i do next multiply it ?

11. perl

The idea here is to code it this way $$\begin{bmatrix} 1 & -2 \\ -3& 7 \end{bmatrix} \cdot \begin{bmatrix} O & E& Q& E & T & O& \_ &O &G\\ N &\_ & U & S & I & N &T &\_ &O \end{bmatrix}$$

12. perl

do you agree with that so far, we just need to change the letters to numbers now

13. anonymous

oh thats all we have to do ?

14. perl

change to numbers and multiply, yes

15. anonymous

okay i think i got it now

16. anonymous

but where did you get all those letters from ?

17. perl

18. anonymous

ok

19. anonymous

do i replace the _ with a zero ?

20. perl
21. perl

right

22. anonymous

okay i seee lol ....

23. perl

here is an example http://aix1.uottawa.ca/~jkhoury/cryptography.htm

24. anonymous

oh that's what you meant by using column vectors

25. perl

right, the only difference they used number 27 for _ and we used 0

26. anonymous

yeah , so when you decode it ,it'll turn into letters or a phrase

27. perl

right

28. anonymous

okay i understand how to do it , it's going to take me a minute to get my answer soo thanks for helping me understand it .