[venkat jothi]

The number of ways to arrange n books  $= n!$

the number of ways to arrange books in which two books are always together $=(n-1)! \times 2!$

the number of ways to arrange books in which two books are not together $=n!- (n-1)!\times 2!$

by simplification we get $(n-2)\times (n-1)!$

[venkat jothi]

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[venkat jothi]

here omega is the cube root of unity

[venkat jothi]

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