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If roots of 2x^(2) - 3x + p are 1/alpha...

If roots of `2x^(2) - 3x + p ` are `1/alpha, 1/beta` and that of `2x^(2) - 7x +q = 0` are `1/gamma, 1/delta` are such that `alpha, beta, gamma, delta` are in HP then p+q =

A

5

B

7

C

11

D

13

Text Solution

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The correct Answer is:
To solve the problem step by step, we will follow the reasoning outlined in the video transcript. ### Step 1: Understanding the Roots We are given two quadratic equations: 1. \(2x^2 - 3x + p = 0\) with roots \( \frac{1}{\alpha} \) and \( \frac{1}{\beta} \) 2. \(2x^2 - 7x + q = 0\) with roots \( \frac{1}{\gamma} \) and \( \frac{1}{\delta} \) Since \( \alpha, \beta, \gamma, \delta \) are in Harmonic Progression (HP), their reciprocals \( \frac{1}{\alpha}, \frac{1}{\beta}, \frac{1}{\gamma}, \frac{1}{\delta} \) will be in Arithmetic Progression (AP). ### Step 2: Sum of Roots For the first equation: - The sum of the roots \( \frac{1}{\alpha} + \frac{1}{\beta} = \frac{3}{2} \) For the second equation: - The sum of the roots \( \frac{1}{\gamma} + \frac{1}{\delta} = \frac{7}{2} \) ### Step 3: Expressing in Terms of \( \alpha \) and \( d \) Since \( \frac{1}{\alpha}, \frac{1}{\beta}, \frac{1}{\gamma}, \frac{1}{\delta} \) are in AP, we can express them as: - \( \frac{1}{\beta} = \frac{1}{\alpha} + d \) - \( \frac{1}{\gamma} = \frac{1}{\alpha} + 2d \) - \( \frac{1}{\delta} = \frac{1}{\alpha} + 3d \) ### Step 4: Setting Up Equations From the sum of roots for the first equation: \[ \frac{1}{\alpha} + \left(\frac{1}{\alpha} + d\right) = \frac{3}{2} \] This simplifies to: \[ \frac{2}{\alpha} + d = \frac{3}{2} \quad \text{(1)} \] From the sum of roots for the second equation: \[ \left(\frac{1}{\alpha} + 2d\right) + \left(\frac{1}{\alpha} + 3d\right) = \frac{7}{2} \] This simplifies to: \[ \frac{2}{\alpha} + 5d = \frac{7}{2} \quad \text{(2)} \] ### Step 5: Solving the Equations Now we will solve equations (1) and (2) together. From equation (1): \[ d = \frac{3}{2} - \frac{2}{\alpha} \] Substituting \( d \) in equation (2): \[ \frac{2}{\alpha} + 5\left(\frac{3}{2} - \frac{2}{\alpha}\right) = \frac{7}{2} \] This simplifies to: \[ \frac{2}{\alpha} + \frac{15}{2} - \frac{10}{\alpha} = \frac{7}{2} \] Combining like terms: \[ -\frac{8}{\alpha} + \frac{15}{2} = \frac{7}{2} \] Subtracting \( \frac{15}{2} \) from both sides: \[ -\frac{8}{\alpha} = \frac{7}{2} - \frac{15}{2} = -4 \] Thus: \[ \frac{8}{\alpha} = 4 \implies \alpha = 2 \] ### Step 6: Finding \( p \) and \( q \) Now we can find \( p \) and \( q \). For \( p \): Using the product of roots: \[ \frac{1}{\alpha} \cdot \frac{1}{\beta} = \frac{p}{2} \] We know \( \frac{1}{\alpha} = \frac{1}{2} \) and \( \frac{1}{\beta} = \frac{1}{\alpha} + d = \frac{1}{2} + \frac{1}{2} = 1 \): \[ \frac{1}{2} \cdot 1 = \frac{p}{2} \implies \frac{1}{2} = \frac{p}{2} \implies p = 1 \] For \( q \): Using the product of roots: \[ \frac{1}{\gamma} \cdot \frac{1}{\delta} = \frac{q}{2} \] We have: \[ \frac{1}{\gamma} = \frac{1}{\alpha} + 2d = \frac{1}{2} + 1 = \frac{3}{2} \] \[ \frac{1}{\delta} = \frac{1}{\alpha} + 3d = \frac{1}{2} + \frac{3}{2} = 2 \] Thus: \[ \frac{3}{2} \cdot 2 = \frac{q}{2} \implies 3 = \frac{q}{2} \implies q = 6 \] ### Step 7: Finding \( p + q \) Finally, we calculate: \[ p + q = 1 + 6 = 7 \] ### Final Answer \[ \boxed{7} \]

To solve the problem step by step, we will follow the reasoning outlined in the video transcript. ### Step 1: Understanding the Roots We are given two quadratic equations: 1. \(2x^2 - 3x + p = 0\) with roots \( \frac{1}{\alpha} \) and \( \frac{1}{\beta} \) 2. \(2x^2 - 7x + q = 0\) with roots \( \frac{1}{\gamma} \) and \( \frac{1}{\delta} \) Since \( \alpha, \beta, \gamma, \delta \) are in Harmonic Progression (HP), their reciprocals \( \frac{1}{\alpha}, \frac{1}{\beta}, \frac{1}{\gamma}, \frac{1}{\delta} \) will be in Arithmetic Progression (AP). ...
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