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If one root of the equation (k+1)x2−13kx+7−2k=0(k + 1)x^2 - 13kx + 7 - 2k = 0(k+1)x2−13kx+7−2k=0​ is the reciprocal of the other, then the value
Question

If one root of the equation (k+1)x213kx+72k=0(k + 1)x^2 - 13kx + 7 - 2k = 0​ is the reciprocal of the other, then the value of k
is:

A.

-2

B.

2

C.

-4

D.

4

Correct option is B

Given:

The quadratic equation is:

(k+1)x213kx+72k=0(k+1)x^2 - 13kx + 7 - 2k = 0​​

It is given that one root is the reciprocal of the other.

Concept Used:

If the roots of a quadratic equation are α and 1α\frac{1}{\alpha}​​, then the product of the roots is always 1.
For a quadratic equation of the form ax2+bx+c=0ax^2 + bx + c = 0​, the product of the roots is given by:

α1α=ca=1\alpha \cdot \frac{1}{\alpha} = \frac{c}{a} = 1​​

Solution:

From the given equation:

a = (k+1)

b = -13k

c = 7 - 2k

Now,

ca=1\frac{c}{a} = 1​​

72kk+1=1\frac{7 - 2k}{k+1} = 1​​

7 - 2k = k + 1

7 - 1 = k + 2k

6 = 3k

k = 2

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