In each of the following, determine whether the statement is true or false. If it is true, prove it. If it is false, give an example.
If $x \in A$ and $A \in B,$ then $x \in B$
False
Let $A=\{1,2\}$ and $B=\{1,\{1,2\},\{3\}\}$
Now, $2 \in\{1,2\}$ and $\{1,2\}$ $\in\{\{3\}, 1,\{1,2\}\}$
$\therefore A \in B$
Howerer, $2 \notin\{\{3\}, 1,\{1,2\}\}$
State whether each of the following set is finite or infinite :
The set of numbers which are multiple of $5$
State which of the following sets are finite or infinite :
$\{ x:x \in N$ and ${x^2} = 4\} $
Write the following as intervals :
$\{ x:x \in R,3\, \le \,x\, \le \,4\} $
State which of the following sets are finite or infinite :
$\{ x:x \in N$ and $2x - 1 = 0\} $
What universal set $(s)$ would you propose for each of the following :
The set of isosceles triangles