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Let a,b,c be in AP and k ne 0 be a real ...

Let a,b,c be in AP and `k ne 0` be a real number. Which of following correct ?
(1) ka, kb, kc are in AP
(2) `k-a,k-b,k-c`
(3) `(a)/(k),(b)/(k),(c)/(k)` are in AP
Select the correct answer using the given code below:

A

A)1 and 2 only

B

B)2 and 3 only

C

C)1 and 3 only

D

D)1,2 and 3

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to determine whether the given statements about the sequences formed by \( a, b, c \) (which are in arithmetic progression) are correct. ### Step-by-Step Solution: 1. **Understanding Arithmetic Progression (AP)**: - If \( a, b, c \) are in AP, then \( 2b = a + c \). This means that the middle term \( b \) is the average of \( a \) and \( c \). 2. **Statement 1: \( ka, kb, kc \) are in AP**: - To check if \( ka, kb, kc \) are in AP, we need to verify if \( 2(kb) = ka + kc \). - Substituting \( kb \) gives us: \[ 2(kb) = 2(k \cdot b) = k(2b) \] \[ ka + kc = k(a + c) \] - Since \( 2b = a + c \), we have: \[ k(2b) = k(a + c) \] - Therefore, \( ka, kb, kc \) are in AP. 3. **Statement 2: \( k-a, k-b, k-c \)**: - To check if \( k-a, k-b, k-c \) are in AP, we need to verify if \( 2(k-b) = (k-a) + (k-c) \). - This simplifies to: \[ 2(k-b) = 2k - 2b \] \[ (k-a) + (k-c) = k - a + k - c = 2k - (a + c) \] - Since \( a + c = 2b \) (from the definition of AP), we have: \[ 2k - (a + c) = 2k - 2b \] - Thus, \( k-a, k-b, k-c \) are also in AP. 4. **Statement 3: \( \frac{a}{k}, \frac{b}{k}, \frac{c}{k} \)**: - To check if \( \frac{a}{k}, \frac{b}{k}, \frac{c}{k} \) are in AP, we need to verify if \( 2\left(\frac{b}{k}\right) = \frac{a}{k} + \frac{c}{k} \). - This simplifies to: \[ 2\left(\frac{b}{k}\right) = \frac{2b}{k} \] \[ \frac{a}{k} + \frac{c}{k} = \frac{a + c}{k} \] - Since \( a + c = 2b \), we have: \[ \frac{a + c}{k} = \frac{2b}{k} \] - Thus, \( \frac{a}{k}, \frac{b}{k}, \frac{c}{k} \) are also in AP. ### Conclusion: All three statements are correct. Therefore, the correct answer is option D: 1, 2, and 3.
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