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JEE Main20199 Apr 2019Morning ShiftMathematicsQuadratic EquationActual

Let p , q ∈ Q . If 2 - 3 is a root of the quadratic equation x 2 + p x + q = 0 , then

Options

  1. Ap 2 – 4 q + 12 = 0
  2. Bq 2 + 4 p + 14 = 0
  3. Cp 2 – 4 q – 12 = 0
  4. Dq 2 – 4 p – 16 = 0

Correct answer

C. p 2 – 4 q – 12 = 0

Step-by-step solution

In given equation x 2 + p x + q = 0 ,   p ,   q ∈ Q . And, we know that the irrational roots of a quadratic equation exist in conjugate pair, if the coefficients are rational. Thus, if one root of the equation x 2 + p x + q = 0 is 2 - 3 , then, the other root will be 2 + 3 . We know that the sum and product of the roots of a quadratic equation a x 2 + b x + c = 0 are respectively - b a and c a . Therefore, the sum of roots 2 + 3 + 2 - 3 = - p ⇒ p = - 4 And, the product of roots 2 + 3 2 - 3 = q

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