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    If x2+1x2=10x^2+\frac{1}{x^2}=10x2+x21​=10​, then what is the value of x4+1x4x^4+\frac{1}{x^4}x4+x41​​ ?
    Question

    If x2+1x2=10x^2+\frac{1}{x^2}=10​, then what is the value of x4+1x4x^4+\frac{1}{x^4}​ ?

    A.

    102

    B.

    100

    C.

    98

    D.

    96

    Correct option is C

    Given:

    x2+1x2=10x^2+\frac{1}{x^2}=10 ​ 

    x4+1x4x^4+\frac{1}{x^4}

    Formula Used:

    To find x4+1x4, we use the identity:x4+1x4=(x2+1x2)22\text{To find } x^4 + \frac{1}{x^4}, \text{ we use the identity:} \\x^4 + \frac{1}{x^4} = \left(x^2 + \frac{1}{x^2}\right)^2 - 2

    Solution:

    (x2+1x2)2=102=100Now,x4+1x4=1002=98\left(x^2 + \frac{1}{x^2}\right)^2 = 10^2 = 100 \\\text{Now,} \\x^4 + \frac{1}{x^4} = 100 - 2 = 98

    ​Final Answer:
    (c) 98

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