Let $U=\{1,2,3,4,5,6\}, A=\{2,3\}$ and $B=\{3,4,5\}$
Find $A^{\prime}, B^{\prime}, A^{\prime} \cap B^{\prime}, A \cup B$ and hence show that $(A \cup B)^{\prime}=A^{\prime} \cap B^{\prime}$
Clearly $A ^{\prime}=\{1,4,5,6\}, B ^{\prime}=\{1,2,6\} .$ Hence $A ^{\prime} \cap B ^{\prime}=\{1,6\}$
Also $A \cup B = \{ 2,3,4,5\} ,$ so that ${(A \cup B)^\prime } = \{ 1,6\} $
$( A \cup B )^{\prime}=\{1,6\}= A ^{\prime} \cap B ^{\prime}$
It can be shown that the above result is true in general. If $A$ and $B$ are any two subsets of the universal set $U,$ then
${(A \cup B)^\prime } = {A^\prime } \cap {B^\prime }$. Similarly, ${(A \cup B)^\prime } = {A^\prime } \cap {B^\prime }.$ These two results are stated in words as follows:
Let $U=\{1,2,3,4,5,6,7,8,9\}, A=\{1,2,3,4\}, B=\{2,4,6,8\}$ and $C=\{3,4,5,6\} .$ Find
$(A \cup C)^{\prime}$
Taking the set of natural numbers as the universal set, write down the complements of the following sets:
$\{ x:x \in N$ and $2x + 1\, > \,10\} $
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$\{x: 2 x+5=9\}$
If $U=\{a, b, c, d, e, f, g, h\},$ find the complements of the following sets:
$A=\{a, b, c\}$
Taking the set of natural numbers as the universal set, write down the complements of the following sets:
$\{ x:x$ is a perfect square $\} $