(a) Show that for a demand function of the form (p) =p, where c and n are positive constants, the elasticity is constant. (Hint: Determine D'(p) and substitute into the formula for E(p).) (b) What type of demand function has elasticity equal to 1 for every value of p?

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### Demand Function and Elasticity

#### (a) Proof of Constant Elasticity for a Given Demand Function

**Problem Statement:**

Show that for a demand function of the form 
\[ D(p) = \frac{c}{p^n} \]
where \( c \) and \( n \) are positive constants, the elasticity is constant. *(Hint: Determine \( D'(p) \) and substitute into the formula for \( E(p) \).)*

**Solution:**

1. **Determine the derivative \( D'(p) \):**
   
   The demand function is given by
   \[ D(p) = \frac{c}{p^n} \]
   
   Taking the first derivative with respect to \( p \):
   \[ D'(p) = \frac{d}{dp} \left( \frac{c}{p^n} \right) \]
   \[ D'(p) = \frac{d}{dp} \left( c \cdot p^{-n} \right) \]
   \[ D'(p) = c \cdot (-n) \cdot p^{-n-1} \]
   \[ D'(p) = -nc \cdot p^{-n-1} \]

2. **Substitute into the elasticity formula \( E(p) \):**
   
   The formula for elasticity \( E(p) \) is:
   \[ E(p) = \frac{p}{D(p)} \cdot \frac{dD(p)}{dp} \]
   
   Substituting \( D(p) \) and \( D'(p) \) into this formula:
   \[ E(p) = \frac{p}{\frac{c}{p^n}} \cdot (-nc \cdot p^{-n-1}) \]
   
   Simplifying the expression:
   \[ E(p) = \frac{p \cdot p^n}{c} \cdot (-nc \cdot p^{-n-1}) \]
   \[ E(p) = \frac{p^{n+1}}{c} \cdot (-nc) \cdot p^{-n-1} \]
   \[ E(p) = (-nc) \cdot \frac{p^{n+1-n-1}}{c} \]
   \[ E(p)
Transcribed Image Text:### Demand Function and Elasticity #### (a) Proof of Constant Elasticity for a Given Demand Function **Problem Statement:** Show that for a demand function of the form \[ D(p) = \frac{c}{p^n} \] where \( c \) and \( n \) are positive constants, the elasticity is constant. *(Hint: Determine \( D'(p) \) and substitute into the formula for \( E(p) \).)* **Solution:** 1. **Determine the derivative \( D'(p) \):** The demand function is given by \[ D(p) = \frac{c}{p^n} \] Taking the first derivative with respect to \( p \): \[ D'(p) = \frac{d}{dp} \left( \frac{c}{p^n} \right) \] \[ D'(p) = \frac{d}{dp} \left( c \cdot p^{-n} \right) \] \[ D'(p) = c \cdot (-n) \cdot p^{-n-1} \] \[ D'(p) = -nc \cdot p^{-n-1} \] 2. **Substitute into the elasticity formula \( E(p) \):** The formula for elasticity \( E(p) \) is: \[ E(p) = \frac{p}{D(p)} \cdot \frac{dD(p)}{dp} \] Substituting \( D(p) \) and \( D'(p) \) into this formula: \[ E(p) = \frac{p}{\frac{c}{p^n}} \cdot (-nc \cdot p^{-n-1}) \] Simplifying the expression: \[ E(p) = \frac{p \cdot p^n}{c} \cdot (-nc \cdot p^{-n-1}) \] \[ E(p) = \frac{p^{n+1}}{c} \cdot (-nc) \cdot p^{-n-1} \] \[ E(p) = (-nc) \cdot \frac{p^{n+1-n-1}}{c} \] \[ E(p)
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