(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

This is a worked problem:

[PLAIN]http://img409.imageshack.us/img409/4821/14091194.gif [Broken]

3. The attempt at a solution

In the answer, how did they get from [tex](1 3 4 9)^7(2 6 8)^7[/tex] to [tex](1 3 4 9)^{-1}(2 6 8)[/tex]?

I know that [tex]\tau^7[/tex] means the permutation [tex]\tau[/tex] repeated 7 times. But I just don't understand why they changed "7" to "-1" on the first cycle and changed "7" to "1" on the second. They are probably using a shortcut but I can't follow it...

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# Homework Help: Permutation Algebra

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