1. **Problem Statement:**
Find the union, intersection, difference of sets A, B, C and verify De Morgan's law using Venn diagrams.
2. **Given Sets:**
$A = \{1,2,3,4,5\}$, $B = \{3,4,5,6,7\}$, $C = \{5,6,7,8\}$
3. **Formulas and Rules:**
- Union: $A \cup B = \{x | x \in A \text{ or } x \in B\}$
- Intersection: $A \cap B = \{x | x \in A \text{ and } x \in B\}$
- Difference: $A - B = \{x | x \in A \text{ and } x \notin B\}$
- Complement: $A' = U - A$ where $U$ is the universal set
- De Morgan's Law: $(A \cup B)' = A' \cap B'$
4. **Step-by-step Solutions:**
**i) Find $A \cup B$:**
Combine all unique elements from $A$ and $B$:
$$A \cup B = \{1,2,3,4,5,6,7\}$$
**ii) Find $A \cap B$:**
Find common elements in $A$ and $B$:
$$A \cap B = \{3,4,5\}$$
**iii) Find $(A \cup B) \cap C$:**
First find $A \cup B$ as above, then intersect with $C$:
$$ (A \cup B) \cap C = \{5,6,7\} $$
**iv) Find $A - B$:**
Elements in $A$ not in $B$:
$$ A - B = \{1,2\} $$
5. **Verify De Morgan's Law $(A \cup B)' = A' \cap B'$:**
- Universal set $U = \{1,2,3,4,5,6,7,8\}$
- $A' = U - A = \{6,7,8\}$
- $B' = U - B = \{1,2,8\}$
- $A' \cap B' = \{8\}$
- $A \cup B = \{1,2,3,4,5,6,7\}$
- $(A \cup B)' = U - (A \cup B) = \{8\}$
Since $(A \cup B)' = A' \cap B' = \{8\}$, De Morgan's law is verified.
6. **Find $A' \cap (A \cup B)$:**
- $A' = U - A = \{2,4,6,7,8\}$
- $A \cup B = \{1,2,3,4,5,6,7\}$
- Intersection:
$$ A' \cap (A \cup B) = \{2,4,6,7\} $$
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**Summary:**
- $A \cup B = \{1,2,3,4,5,6,7\}$
- $A \cap B = \{3,4,5\}$
- $(A \cup B) \cap C = \{5,6,7\}$
- $A - B = \{1,2\}$
- De Morgan's law verified: $(A \cup B)' = A' \cap B' = \{8\}$
- $A' \cap (A \cup B) = \{2,4,6,7\}$
Set Operations 1A65F2
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