Set Operations 0609Ce
1. **Problem Statement:**
Given three sets:
- $A = \{ x \in \mathbb{R} : 2 < x \leq 5 \}$
- $B = \{ x \in \mathbb{R} : x \leq 2 \}$
- $C = \{ x \in \mathbb{R} : -2 \leq x < 3 \}$
We need to find and sketch the following sets on the real number line:
(i) $A \cup B'$
(ii) $A' \cap B$
(iii) $(A \cup B) \cap C$
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2. **Recall important rules:**
- The complement of a set $S$, denoted $S'$, is all real numbers not in $S$.
- Union $\cup$ means all elements in either set.
- Intersection $\cap$ means elements common to both sets.
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3. **Find $B'$:**
Since $B = \{ x : x \leq 2 \}$, its complement is
$$B' = \{ x : x > 2 \}$$
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4. **Calculate (i) $A \cup B'$:**
- $A = \{ x : 2 < x \leq 5 \}$
- $B' = \{ x : x > 2 \}$
Since $B'$ includes all $x > 2$, and $A$ is a subset of $B'$, their union is simply:
$$A \cup B' = \{ x : x > 2 \}$$
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5. **Calculate (ii) $A' \cap B$:**
- $A' = \{ x : x \leq 2 \text{ or } x > 5 \}$ (complement of $A$)
- $B = \{ x : x \leq 2 \}$
Intersection is numbers in both $A'$ and $B$:
$$A' \cap B = \{ x : x \leq 2 \}$$
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6. **Calculate (iii) $(A \cup B) \cap C$:**
- $A \cup B = \{ x : x \leq 5 \}$ (since $B$ covers $x \leq 2$ and $A$ covers $2 < x \leq 5$)
- $C = \{ x : -2 \leq x < 3 \}$
Intersection:
$$ (A \cup B) \cap C = \{ x : -2 \leq x < 3 \}$$
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**Final answers:**
- (i) $A \cup B' = \{ x : x > 2 \}$
- (ii) $A' \cap B = \{ x : x \leq 2 \}$
- (iii) $(A \cup B) \cap C = \{ x : -2 \leq x < 3 \}$
These sets can be sketched on the real number line accordingly.