Question:easy

Let \(\alpha\) and \(\beta\) be the two distinct roots of the equation of 2x2-6x+k=0, such that (\(\alpha+\beta\)) and \(\alpha\beta\) are the distinct roots of the equation x2+px+p=0, then, the value of 8(k-p) ?

Updated On: Nov 25, 2025
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The Correct Option is C

Solution and Explanation

Given: α and β are distinct roots of \( 2x^2 - 6x + k = 0 \).

From Vieta's formulas, the product of roots is \( \alpha\beta = \frac{k}{2} \) and the sum of roots is \( \alpha + \beta = \frac{-(-6)}{2} = 3 \).

The roots of the equation \( x^2 + px + p = 0 \) are \( r_1 = \alpha + \beta = 3 \) and \( r_2 = \alpha\beta = \frac{k}{2} \).

Using the sum of roots for the second equation: \( r_1 + r_2 = 3 + \frac{k}{2} = -p \) (1).

Using the product of roots for the second equation: \( r_1 \cdot r_2 = 3 \cdot \frac{k}{2} = p \) (2).

Substitute \( p = \frac{3k}{2} \) from (2) into (1): \( 3 + \frac{k}{2} = -\frac{3k}{2} \).

Multiply by 2: \( 6 + k = -3k \Rightarrow 6 = -4k \Rightarrow k = -\frac{3}{2} \).

Substitute \( k = -\frac{3}{2} \) into (2) to find p: \( p = \frac{3}{2} \cdot \left(-\frac{3}{2}\right) = -\frac{9}{4} \).

Calculate \( 8(k - p) \): \( 8\left(-\frac{3}{2} - (-\frac{9}{4})\right) = 8\left(-\frac{3}{2} + \frac{9}{4}\right) \).

Convert to a common denominator: \( 8\left(-\frac{6}{4} + \frac{9}{4}\right) = 8\left(\frac{3}{4}\right) = \boxed{6} \).

Final Answer: 6 (Option C)

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