New 55% Off on All Courses - Enroll Now! Click Here

    Question

    If for non-zero x, x² - 4x - 1 = 0, what is the value

    of x² + 1/x²?
    A 4 Correct Answer Incorrect Answer
    B 10 Correct Answer Incorrect Answer
    C 12 Correct Answer Incorrect Answer
    D 18 Correct Answer Incorrect Answer

    Solution

    Given, x² - 4x - 1 = 0 ⇒ x - 4 - 1/x = 0   [Dividing both sides by x] ⇒ x - 1/x = 4 ⇒ (x - 1/x)² = 4²   [Squaring on both sides] ⇒ x² + 1/x² - 2 = 16 ⇒ x² + 1/x² = 18

    Practice Next

    Relevant for Exams: