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Quadratic Equation and Inequalities question

2002 · Shift 0 · Q101
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Quadratic Equation and Inequalities question

2002 · Shift 0 · Q101

JEE MainMathematicsQuadratic Equation and InequalitiesMCQ+4 / −1
Product of real roots of equation t2x2+∣x∣+9=0{t^2}{x^2} + \left| x \right| + 9 = 0t2x2+∣x∣+9=0
  1. A
    is always positive
  2. B
    is always negative
  3. C
    does not exist
  4. D
    none of these
View written solutionFree

Correct answer: C

  1. Given equation

    t2x2+∣x∣+9=0t^2x^2 + |x| + 9 = 0t2x2+∣x∣+9=0

    We are asked about the product of real roots.

  2. Observe each term

    For any real xxx and real ttt:

    • t2x2≥0t^2x^2 \ge 0t2x2≥0 because a square is always non-negative.
    • ∣x∣≥0|x| \ge 0∣x∣≥0 by definition of modulus.
    • 9>09 > 09>0 always.

    Therefore,

    t2x2+∣x∣+9≥0+0+9=9>0t^2x^2 + |x| + 9 \ge 0 + 0 + 9 = 9 > 0t2x2+∣x∣+9≥0+0+9=9>0

  3. Can the equation ever be satisfied?

    The left-hand side is always strictly positive:

    t2x2+∣x∣+9>0t^2x^2 + |x| + 9 > 0t2x2+∣x∣+9>0

    Hence it can never be equal to 000 for any real xxx.

    So the equation has no real roots.

  4. Product of real roots

    Since there are no real roots, the product of real roots is not defined / does not exist.

  5. Check options

    • A: is always positive — Incorrect, because there are no real roots.
    • B: is always negative — Incorrect.
    • C: does not exist — Correct.
    • D: none of these — Incorrect.
  6. Comparison with stored answer

    The stored correct answer is A, but our derivation shows the correct option is C.

    So the stored answer appears to be incorrect.

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