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$16(x^4 + \frac{1}{x^4}) - 257 = 0$

What is \(\left(x^2 + \frac{1}{x^2}\right)\) equal to ?

This question was previously asked in
CDS 1 2026 Maths Question Paper (12-Apr-2026)
The correct answer is

\(\frac{17}{4}\)

To solve the problem, we need to find the value of \(x^2 + \frac{1}{x^2}\) given the equation:

\(16(x^4 + \frac{1}{x^4}) - 257 = 0.\)

Let's proceed step-by-step:

  1. \(16(x^4 + \frac{1}{x^4}) = 257\)
  2. Simplifying, we get:
    • \(x^4 + \frac{1}{x^4} = \frac{257}{16}\)
  3. Recall the identity:
    • \((x^2 + \frac{1}{x^2})^2 = x^4 + \frac{1}{x^4} + 2\)
  4. Now, substitute the value we found:
    • \((x^2 + \frac{1}{x^2})^2 = \frac{257}{16} + 2\)
  5. Convert and simplify:
    • \(\frac{257}{16} + 2 = \frac{257}{16} + \frac{32}{16} = \frac{257 + 32}{16} = \frac{289}{16}\)
  6. Thus,
    • \((x^2 + \frac{1}{x^2})^2 = \frac{289}{16}\)
  7. Taking the square root on both sides gives:
    • \(x^2 + \frac{1}{x^2} = \sqrt{\frac{289}{16}} = \frac{\sqrt{289}}{\sqrt{16}} = \frac{17}{4}\)

Finally, the correct answer to the problem according to computations and given options is \(\frac{17}{4}\)

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Important Questions from Algebra

  1. The difference between the two positive numbers x and y where x > y, is 25% of x. If the value of y is 15, then the value of x is:

  2. If p2 + q2 - r2 = 0, then the value of (p6 + q6 - r6) ÷ p2q2r2 is:

  3. If √2 + √x = √3, then the value of x is equal to:

  4. The sum of two numbers is 20 and their difference is 2.5. Ratio of these numbers will be:

  5. If \(\rm \frac{\sqrt{19 - x \sqrt{12}}}{1} = \sqrt 4 - \sqrt 3\)  then the value of x is equal to:

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