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why  4^10 is done.

solution:

Please explain the last portion why 4^ 10 is done.

The binary relation is defined on a set $A$ which is a function from $A*A$ to $A$ .

So , Number of element in $A*A$= $4*4=16$

So total number of binary operation is $4^{16}$.

It consist of all the binary relations but we need only commutative .

Commutative pair = no of symmetric relation which is first take all the reflexive pairs in $n$ ways then take symmetric pairs n(n-1)/2 .

So total =n+n(n-1)/2= n(n+1)/2.

putting n=4 ,we get 4*5/2=10 .

so total we have $4^{10}$ commutative relation.
Okay I have a question here, what if they ask me for the no. of associative functions?

Its a nice question

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