Which of the following are examples of the null set
$\{ y:y$ is a point common to any two parallellines $\} $
If $Q = \left\{ {x:x = {1 \over y},\,{\rm{where \,\,}}y \in N} \right\}$, then
Let $A=\{1,2,\{3,4\}, 5\} .$ Which of the following statements are incorrect and why ?
$\{1,2,5\}\subset A$
Which of the following are sets ? Justify your answer.
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Write the following as intervals :
$\{ x:x \in R,0\, \le \,x\, < \,7\} $