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Black Book Advanced Problems in MathematicsMathematicsQuadratic Equation

If the equation x^2 + ax + 12 = 0, x^2 + bx + 15 = 0 and x^2 + (a + b)x + 36 = 0 have a common positive root, then b - 2a is equal to.

Options

  1. A-6
  2. B22
  3. C6
  4. D-22.

Correct answer

C. 6

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