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Home Aptitude Quadratic Equation Comments

  • Question
  • In solving a problem, one student makes a mistake in the coefficient of the first degree term and obtain -9 and -1 for the roots. Another student makes a mistake in the constant term of the equation and obtains 8 and 2 for the roots. The correct equation was


  • Options
  • A. x2 + 10x + 9 = 0
  • B. x2 - 10x + 16 = 0
  • C. x2 - 10x + 9 = 0
  • D. None of the above

  • Correct Answer
  • x2 - 10x + 9 = 0 

    Explanation

    When mistake is done in first degree term, the roots of the equation are -9 and -1.
    ? Equation
    (x+ 1) (x + 9) = x2 + 10x + 9 ...(i)
    When mistake is done in constant term, the roots of equation are 8 and 2.
    ? Equation is
    (x - 2) (x - 8) = x2 - 10x + 16 .....(ii)
    ? Required equation from Eqs. (i) and (ii) is
    = x2 - 10x + 9
    Also we see in both the cases 1st degree term is same with oposite sign i.e., in such questions we should take data from given conditions and find the correct equation.


  • Quadratic Equation problems


    Search Results


    • 1. 
      If ? and ? are the roots of the equation 8x 2 - 3x + 27 = 0, find the value of (? 2/?) 1/3 + (? 2/?) 1/3

    • Options
    • A. 1/3
    • B. 1/4
    • C. 7/2
    • D. 4
    • Discuss
    • 2. 
      The sum of the roots of the equation x 2 + px + q = 0 is equal to the sum of their squares, then

    • Options
    • A. p2 - q2 = 0
    • B. p2 + q2 = 2q
    • C. p2 + p = 2q
    • D. q2 + q2 = 2p
    • Discuss
    • 3. 
      If a = p / (p + q) and b = q / (p - q), then and ab/a + b is equal to

    • Options
    • A. pq / (p2 + q2)
    • B. (p2 + q2) / pq
    • C. p / (p + q)
    • D. [p / (p + q)]2
    • Discuss
    • 4. 
      If x 2 = 6 + ? 6 + ?6 + ?6 + .... ? , then what is one of the value of x equal to?

    • Options
    • A. 6
    • B. 5
    • C. 4
    • D. 3
    • Discuss
    • 5. 
      If ? and ? are the roots of the equation x 2 - 11x + 24 = 0, find the equation having the roots ? + 2 and ? + 2

    • Options
    • A. x2 + 15x + 24 = 0
    • B. x2 - 15x + 24 = 0
    • C. x2 + 15x - 50 = 0
    • D. x2 + 15x - 60 = 0
    • Discuss
    • 6. 
      If one of the roots of the equation x 2 - bx + c = 0 is the square of the other, then which of the following option is correct?

    • Options
    • A. b3 = 3bc + c2 + c
    • B. c3 = 3bc + b2 + b
    • C. 3bc = c3 + b2 + b
    • D. 3bc = c3 + b3 + b2
    • Discuss
    • 7. 
      Two students A and B solve an equation of the from x 2 + px + q = 0. A starts with a wrong value of p and obtains the roots as 2 and 6. B starts with a wrong value of q and gets the roots as 2 and -9. What are the correct roots of the equation?

    • Options
    • A. 3 and - 4
    • B. - 3 and - 4
    • C. - 3 and 4
    • D. 3 and 4
    • Discuss
    • 8. 
      If x = ? ?(5 + 1)/?(5 - 1), then x 2 - x - 1 is equal to

    • Options
    • A. 0
    • B. 1
    • C. 2
    • D. 5
    • Discuss
    • 9. 
      If ?, ? are the roots of the equation x2 - 5x + 6 = 0, construct a quadratic equation whose roots are
      1
      ,
      1
      .
      ?
      ?

    • Options
    • A. 6x2 + 5x - 1 = 0
    • B. 6x2 - 5x - 1 = 0
    • C. 6x2 - 5x + 1 = 0
    • D. 6x2 + 5x + 1 = 0
    • Discuss
    • 10. 
      Consider the equation px2 + qx + r = 0, where p, q, r are real. The roots are equal in magnitude but opposite in sign when :

    • Options
    • A. q = 0, r = 0, p ? 0
    • B. p = 0, qr ? 0
    • C. r = 0, pr ? 0
    • D. q = 0, pr ? 0
    • Discuss


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