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Finding the trace of the inverse of a 2x2 matrix in (mod 26)

  • Thread starter Woolyabyss
  • Start date
  • #1
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Homework Statement


.......(2 , 3)
A =
......(1 , 3)

Find the trace of A^(-1)

Homework Equations


(a , b)................................(d , -b)
.........^(-1) = (ad-bc)^(-1)*
(c , d).................................(-c, a)

The Attempt at a Solution


..............(3 , -3)
A^-1 = 9*
..............(-1. 2)

(In mod 26)

........... (1, -1)
=
.......... (-9, 18)

Trace of A^(-1) = 1 + 18 = 19


The solution I was given said the trace is 18 but I can't seem to find where I went wrong.
Any help would be appreciated.
(Also sorry about the horrible way I wrote the matrices)
 

Answers and Replies

  • #2
RUber
Homework Helper
1,687
344
I don't see any issue with what you have. You can verify that your solution is the inverse, so it may be that the solution is off.
 
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