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    If one zero of the polynomial f(x)=(k² + 4)x² + 13x + 4k is reciprocal of the other zero, then value of k is :
    Question

    If one zero of the polynomial f(x)=(k² + 4)x² + 13x + 4k is reciprocal of the other zero, then value of k is :

    A.

    -2

    B.

    -1

    C.

    2

    D.

    1

    Correct option is C

    Solution:


    Given:

    The polynomial is f(x) = (k2+4)x2+13x+4k(k^2 + 4)x^2 + 13x + 4k​ . One zero of the polynomial is the reciprocal of the other.

    Condition for Reciprocal Roots:

    If one root is the reciprocal of the other, the product of the roots is:

    Product of roots=1\text{Product of roots} = 1​​


    For a quadratic polynomial ax2+bx+cax^2 + bx + c​ , the product of the roots is:

    Product of roots=ca\text{Product of roots} = \frac{c}{a}​​


    Coefficients of the Polynomial:

    Coefficient of x2:a=k2+4x^2 : a = k^2 + 4
     Constant term: c = 4k

    Substitute these values into the condition:

    ca=1\frac{c}{a} = 1​​


    Solve for k :


    4kk2+4=1\frac{4k}{k^2 + 4} = 1​​

    Multiply through by k2k^2​ + 4 (assuming k2+40k^2 + 4 \neq 0​ ):

    4k = k2k^2​ + 4

    Rearrange:

    k2k^2​ - 4k + 4 = 0

    Factorize:

    (k2)2(k - 2)^2 ​= 0

    Solve:

    k = 2


    Final Answer:

    Option C: 2

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