Using that for any sets $\mathrm{A}$ and $\mathrm{B},$
$A \cup(A \cap B)=A$
To show: $A \cup(A \cap B)=A$
We know that
$A \subset A$
$A \cap B \subset A$
$\therefore A \cup(A \cap B) \subset A$ ..........$(1)$
Also, $A \subset A \cup(A \cap B)$ ..............$(2)$
$\therefore$ From $(1)$ and $(2), A \cup(A \cap B)=A$
Is it true that for any sets $\mathrm{A}$ and $\mathrm{B}, P(A) \cup P(B)=P(A \cup B) ?$ Justify your answer.
Show that $A \cap B=A \cap C$ need not imply $B = C$
If $S$ and $T$ are two sets such that $S$ has $21$ elements, $T$ has $32$ elements, and $S$ $\cap \,T$ has $11$ elements, how many elements does $S\, \cup$ $T$ have?
If $aN = \{ ax:x \in N\} ,$ then the set $3N \cap 7N$ is .....$N$
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