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    If x+1xx + \frac{1}{x}x+x1​ = 4 , then find the value of x2+1x2x ^2+ \frac{1}{x^2}x2+x21​​​
    Question

    If x+1xx + \frac{1}{x} = 4 , then find the value of x2+1x2x ^2+ \frac{1}{x^2}​​

    A.

    16

    B.

    14

    C.

    12

    D.

    18

    Correct option is B

    Given: 

    x+1x=4x+\frac{1}{x}=4​​

    Solution:

    The given equation: x+1x=4x+\frac{1}{x}=4 

    ​Square both sides of the equation: 

    (x+1x)2=42(x+\frac{1}{x})^2=4^2 

    x2+2×x×1x+1x2=16x^2+2\times x \times\frac{1}{x}+\frac{1}{x^2}=16 

    x2+2+1x2=16x^2+2+\frac{1}{x^2}=16 

    ​Subtract 2 from both sides :  x2+1x2x^2+\frac{1}{x^2} 

    x2+1x2=162x^2+\frac{1}{x^2}=16 -2​​

    x2+1x2x^2+\frac{1}{x^2} =14

    Thus, correct answer is (b) 14

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