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    Question

    Given that x8-34x4+1=0, x>0.

    What is the value of (x3+ x-3)?
    A 5√8 Correct Answer Incorrect Answer
    B 5 √6 Correct Answer Incorrect Answer
    C 6√8 Correct Answer Incorrect Answer
    D 6√6 Correct Answer Incorrect Answer

    Solution

    Divide given equation by x4 = x4+ 1/x4= 34 = add 2 both side x2+ 1/x2= 6 = add both the side again = x + 1/x = √8 = x3+ 1/x3= 8√8 – 3 × √8 = 5√8

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