Practicing Success
If the numbers of different reflexive relations on a set A is equal to the number of different symmetric relations on set A, then the numbers of elements in A is _____. |
3 |
Let there be n elements in set A. Then, Number of different reflexive relations on A = $2^{n^2-n}$ Number of different symmetric relations on A = $A=2^{\frac{n^2+n}{2}}$ It is given that $2^{n^2-n}=2^{\frac{n^2+n}{2}}$ $⇒n^2-n=\frac{n^2+n}{2}⇒n^2-3n=0⇒n(n-3)=0⇒n=3$ |