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Home Aptitude Quadratic Equation See What Others Are Saying!
  • Question
  • For what value of k, the equation x 2 + 2(k - 4) x + 2k = 0 has equal roots?


  • Options
  • A. 6 and 4
  • B. 8 and 2
  • C. 10 and 4
  • D. 12 and 2

  • Correct Answer
  • 8 and 2 

    Explanation

    Given equation is
    x2 + 2(k - 4)x + 2k = 0
    On comparing with ax2 + bx + c = 0
    Here, a = 1, b = 2(k -4), c = 2k
    Since, the root are equal, we have D = 0.
    b2 - 4ac = 0
    ? 4(k - 4)2 - 8k = 0
    4(k2 + 16 - 8k) - 8k = 0
    ? 4k2 + 64 - 32k - 8k = 0
    ? 4k2 - 40k + 64 = 0
    ? k2 - 10k + 16 = 0
    ? k2 - 8k - 2k + 16 = 0
    ? k(k - 8) -2 (k - 8) = 0
    ? (k - 8) (k - 2) = 0
    Hence, the value of k 8 or 2.


  • More questions

    • 1. 
      The median for the data 2, 4, 6, 8, 10, 12, 14 is

    • Options
    • A. 6
    • B. 8
    • C. 9.5
    • D. 10
    • Discuss
    • 2. 
      The value of 47 / 10000 is?

    • Options
    • A. .0047
    • B. .0470
    • C. .00047
    • D. .000047
    • Discuss
    • 3. If 4x = 18y, then the value of ( x/y - 1) is

    • Options
    • A. 1 3
    • B. 7 2
    • C. 2 3
    • D. 3 2
    • Discuss
    • 4. 
      If the price of 23 toys is Rs. 276, then what will the price (Rs.) of 12 toys?

    • Options
    • A. 144
    • B. 158
    • C. 159
    • D. 166
    • Discuss
    • 5. 
      .02 =(......?.....)%

    • Options
    • A. 20
    • B. 2
    • C. .02
    • D. .2
    • Discuss
    • 6. 
      If 36 men can do a piece of work in 25 hours, in how many hours will 15 men do it?

    • Options
    • A. 45
    • B. 55
    • C. 60
    • D. 72
    • Discuss
    • 7. 
      2?63 / 11 =233

    • Options
    • A. 4
    • B. 3
    • C. 6
    • D. 5
    • Discuss
    • 8. 
      When 121012 is divided by 12, the remainder is

    • Options
    • A. 0
    • B. 2
    • C. 3
    • D. 4
    • Discuss
    • 9. 
      Aarti can do a piece of work in 6 days. In how many days will she complete three time of work of same type?

    • Options
    • A. 18 days
    • B. 21 days
    • C. 3 days
    • D. 6 days
    • Discuss
    • 10. 
      750.0003 ÷ 19.999 =?

    • Options
    • A. 49
    • B. 18
    • C. 22
    • D. 38
    • Discuss


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