1.Relation and Function
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समुच्चय $\{1,2,3,4\}$ पर परिभाषित ऐसे संबंधों, जो सममित हैं, पर स्वतुल्य नहीं हैं, की संख्या है ..........

A

$950$

B

$940$

C

$960$

D

$965$

(JEE MAIN-2024)

Solution

Total number of relation both symmetric and reflexive $=2^{\frac{\mathrm{n}^2-\mathrm{n}}{2}}$

Total number of symmetric relation $=2^{\left(\frac{\mathrm{n}^2+\mathrm{n}}{2}\right)}$

$\Rightarrow$ Then number of symmetric relation which are not reflexive

$ \Rightarrow $ $ 2^{\frac{n(n+1)}{2}}-2^{\frac{n(n-1)}{2}}$

$ \Rightarrow $ $2^{10}-2^6 $

$\Rightarrow $  $1024-64 $

$ =960$

Standard 12
Mathematics

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