Derangement : Recursive relation proof (formula): Dn=(n-1)(Dn-1+Dn-2)

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[Mathsmerizing]

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[DilshanIITD]

Thank you sir, the best video i needed to know the proof

[sword]

Proof(understanding) begins at 3:45 ;
Good example.

[vizagdiaries]

Way of Teaching Excellent 👌 simply superb, voice also

[spiderjerusalem]

could you verifty the recurrence relation of "number of permutations with k fixed points" (the generalization deragement formula, denoted D(n, r, k). r-elements permutation subsets are to be arranged from the given n elements, and there are k fixed pointa)
D(n, r, k) = D(n-1, r-1, k-1)+(n-1)D(n-1, r-1, k) + (r-1)(D(n-2, r-2, k)-D(n-2, r-2, k-1))

[pranavgaur]

But I don't understand why do we need to break it into those two cases. Why is (n-1)*(Dn-1) not sufficient?

[rishavsikdar]

i had a question when we are selecting any one of the n objects to assign it one of the n-1 houses shouldnt the derangements then be n*n-1*(dn-1+dn-2)?

[prashantbharati]

Background music is really wholesome, almost distracting

[_varshaa_]

Please remove the background music🙏
Great explanation though👍👍

[himanshujoshi]

But when we take recursive soln for n-1 and n-2 wont the solutions overlap? for ex for n=4 we may get 4321 and 4321 in both n-1 and n-2 recursive solution

[idk]

The fact that jee advanced paper ('14) question was inspired from this concept is great

[kironpaul]

if you can remove the background music the video will get more views
that it have..

[bhoomeendra]

how is this last situation where p1 is not able to go to h1 and hk similar to Derangment of n-1 people

[ajitkumar-sgbd]

Thank you sir for these videos, its really nice