i. Which of the following relations f: Q → Q define a mapping? In each case, supply a reason why f is or is not a mapping. p+1 3p a. f(p/q): = b. f(p/q) = = p-2 3q p+q Р c. f(p/q): d. f(p/q) = 32²2-22 q² 7q² =

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### Identifying Mappings in Relations from Rational Numbers to Rational Numbers

This exercise focuses on evaluating whether given relations \( f : \mathbb{Q} \to \mathbb{Q} \) define a mapping. In each case, we are required to justify whether \( f \) is or is not a mapping.

#### Definitions and Relations
Consider the following functions \( f \), where \( p \) and \( q \) are rational numbers (\( q \neq 0 \)):

a. \( f(p/q) = \frac{p+1}{p-2} \)

b. \( f(p/q) = \frac{3p}{3q} \)

c. \( f(p/q) = \frac{p+q}{q^2} \)

d. \( f(p/q) = \frac{3p^2}{7q^2} - \frac{p}{q} \)

#### Analysis

##### Option a
**Function:**
\[ f(p/q) = \frac{p+1}{p-2} \]

**Reasoning:**
- To determine if it is a valid function, consider the denominator \( p-2 = 0 \), which implies \( p = 2 \). At \( p = 2 \), the function is undefined because division by zero is not allowed.
- Therefore, \( f(p/q) \) is not defined for all rational numbers, making it not a proper mapping over the domain of all rational numbers \( \mathbb{Q} \).

##### Option b
**Function:**
\[ f(p/q) = \frac{3p}{3q} \]

**Reasoning:**
- Simplify the function: \( \frac{3p}{3q} = \frac{p}{q} \).
- The function essentially maps \( p/q \) to itself, which is well-defined for all rational \( p \) and \( q \) ( \( q \neq 0 \)).
- Hence, \( f(p/q) \) is a valid mapping.

##### Option c
**Function:**
\[ f(p/q) = \frac{p+q}{q^2} \]

**Reasoning:**
- The expression \( \frac{p+q}{q^2} \) is defined for all rational \( p \) and \( q \) ( \( q \neq 0 \
Transcribed Image Text:### Identifying Mappings in Relations from Rational Numbers to Rational Numbers This exercise focuses on evaluating whether given relations \( f : \mathbb{Q} \to \mathbb{Q} \) define a mapping. In each case, we are required to justify whether \( f \) is or is not a mapping. #### Definitions and Relations Consider the following functions \( f \), where \( p \) and \( q \) are rational numbers (\( q \neq 0 \)): a. \( f(p/q) = \frac{p+1}{p-2} \) b. \( f(p/q) = \frac{3p}{3q} \) c. \( f(p/q) = \frac{p+q}{q^2} \) d. \( f(p/q) = \frac{3p^2}{7q^2} - \frac{p}{q} \) #### Analysis ##### Option a **Function:** \[ f(p/q) = \frac{p+1}{p-2} \] **Reasoning:** - To determine if it is a valid function, consider the denominator \( p-2 = 0 \), which implies \( p = 2 \). At \( p = 2 \), the function is undefined because division by zero is not allowed. - Therefore, \( f(p/q) \) is not defined for all rational numbers, making it not a proper mapping over the domain of all rational numbers \( \mathbb{Q} \). ##### Option b **Function:** \[ f(p/q) = \frac{3p}{3q} \] **Reasoning:** - Simplify the function: \( \frac{3p}{3q} = \frac{p}{q} \). - The function essentially maps \( p/q \) to itself, which is well-defined for all rational \( p \) and \( q \) ( \( q \neq 0 \)). - Hence, \( f(p/q) \) is a valid mapping. ##### Option c **Function:** \[ f(p/q) = \frac{p+q}{q^2} \] **Reasoning:** - The expression \( \frac{p+q}{q^2} \) is defined for all rational \( p \) and \( q \) ( \( q \neq 0 \
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