Relations Functions 86B28C
1. **Problem Statement:**
Given sets $A = B = \{1,2,3,4\}$ and relations:
- $R_1 = \{(x,y) \mid x \in A, y \in B, x = y^2 + 1\}$
- $R_2 = \{(x,y) \mid x \in A, y \in B, x$ is even and $y$ is odd$\}$
Find:
(i) The relations $R_1$ and $R_2$ as sets of ordered pairs.
(ii) The domain and range of $R_1$ and $R_2$.
(iii) Whether $R_1$ and $R_2$ represent functions.
2. **Step (i): Write relations as ordered pairs**
- For $R_1$, find all $(x,y)$ with $x = y^2 + 1$ and $x,y \in \{1,2,3,4\}$.
Calculate $y^2 + 1$ for each $y$:
- $y=1 \Rightarrow 1^2+1=2$ (in $A$)
- $y=2 \Rightarrow 4+1=5$ (not in $A$)
- $y=3 \Rightarrow 9+1=10$ (not in $A$)
- $y=4 \Rightarrow 16+1=17$ (not in $A$)
So only $y=1$ gives $x=2$ in $A$.
Thus, $R_1 = \{(2,1)\}$.
- For $R_2$, $x$ is even and $y$ is odd, both in $\{1,2,3,4\}$.
Even $x$: $2,4$.
Odd $y$: $1,3$.
So $R_2 = \{(2,1),(2,3),(4,1),(4,3)\}$.
3. **Step (ii): Domain and Range**
- $R_1$:
- Domain: all $x$ values in $R_1$ = $\{2\}$.
- Range: all $y$ values in $R_1$ = $\{1\}$.
- $R_2$:
- Domain: $\{2,4\}$.
- Range: $\{1,3\}$.
4. **Step (iii): Check if relations are functions**
- A relation is a function if each element in the domain maps to exactly one element in the range.
- $R_1$ has domain $\{2\}$ and maps $2 \to 1$ uniquely, so $R_1$ is a function.
- $R_2$ has domain $\{2,4\}$ but $2$ maps to both $1$ and $3$, and $4$ maps to both $1$ and $3$.
Since elements in domain map to multiple values, $R_2$ is not a function.
**Final answers:**
(i) $R_1 = \{(2,1)\}$, $R_2 = \{(2,1),(2,3),(4,1),(4,3)\}$.
(ii) Domain and range:
- $R_1$: Domain $= \{2\}$, Range $= \{1\}$.
- $R_2$: Domain $= \{2,4\}$, Range $= \{1,3\}$.
(iii) $R_1$ is a function; $R_2$ is not a function.