Sets and their Representation

The fast breeder reactor uses the following moderator

If $A=\left\{1, 3, 5, 7\right\}, B=\left\{2, 4, 6, 8\right\}$ and $C=\left\{3,6,9\right\}$, then verify that $A\cup (B\cap C)=(A\cup B)\cap (A\cup C)$

Let $L$ be the set of all lines in a plane $R$ be the relation in $L$ defined as $R=\left\{\left(L_1,L_2\right):L_1 \text{is perpendicular to} L_2\right\}$. Show that $R$ is symmetric but neither reflexive nor transitive. 

The letters or elements are enclosed in a curl brackets $"\left\{\right\}"$ in set theory.

Write whether the given collection forms a set or not?

High mountains of the world.

Write whether the given collection forms a set or not?

Roots of the equation $x^2-6x+9=0$

Write whether the given collection forms a set or not?

Ten positive integers.

Write whether the given collection forms a set or not?

Prime factors of $2$

Whether the given collection forms a set or not?

Good teachers of India. 

Write whether the given collection forms a set or not?

Factors of $50$.

Which of the following collections forms a set?

Kind people of West Bengal. 

Which of the following collections forms a set?
The letters in the word 'balloon?

Which of the following collections forms a set?
 All prime positive integers less than $50$.

Which of the following collections forms a set?
All integers strictly between $10$ and $20$.

Write the set $\left\{\frac{1}{3}, \frac{3}{5}, \frac{5}{7}, \frac{7}{9}, \frac{9}{11}, \frac{11}{13}, \frac{13}{15}\right\}$ in set builder form.

If $A=\left\{x\mid x^2-4x+4=0\right\},$ then find $\left|A\right|$.

Write the following sets in set builder form.

Letters in the word 'statistics?

Write the following sets in set builder form.

$\left\{1, \frac{1}{2}, \frac{1}{3}, \frac{1}{4}, \dots , \frac{1}{25}\right\}$

Write the following sets in set builder form.

Set of rational numbers strictly between $1$ and $2$ .

Write the following sets in set builder form.

Set of factors of $30$.