plz solve this with full explanation.chapter name functions?/

the number of bijective functions f:A->A,where A={1,2,3} such tht f(1)â‰ 3,f(2)â‰ 1,f(3)â‰ 2
are----??

2 Answers

This is a question of derrangement..

see the thing is that there is nothing special about 3, 1 and 2

we could as well have asked.. no of functions such that f(1)â‰ 1, f(2)â‰ 2 and f(3)â‰ 3 to get the same answer

so teh number of solutions is D(3)=2

If you are not sure of what derangement is read http://en.wikipedia.org/wiki/Derangement

use principle of inclusion and exclusion

famopusly called as PIE

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