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  • Question
  • If x + 1/x = 3, then x5 + 1/x5 is equal to?


  • Options
  • A. 123
  • B. 83
  • C. 92
  • D. 112

  • Correct Answer
  • 123 

    Explanation

    x + 1/x = 3 ........................ (i)
    On squaring both side, we will get
    (x + 1/x)2 = (3)2
    Use the Square algebra formula (a + b)2 = a2 + 2ab + b2
    ? x2 + 1/x2 + 2 = 9
    ? x2 + 1/x2 = 7 ..................(ii)
    Again squaring both sides, we will get
    (x2 + 1/x2)2 = (7)2
    Use the Square algebra formula (a + b)2 = a2 + 2ab + b2
    ? x4 + 1/4 + 2 = 49
    ? x4 + 1/x4 = 47 .....................(iii)
    On cubing the equation (i) both side, we will get
    (x + 1/x)3 = (3)3
    Use the cube algebra formula (a + b)3 = a3 + 3a2b + 3ab2 + b3
    ? x3+ 1/x3 + 3(x + 1/x) = 27
    ? x3 + 1/x3 + 9 = 27 [? (x + 1/x) = 3]
    ? x3 + 1/x3 = 18 ...................(iv)
    On multiplying Eqs. (i) and (iii) , we get
    ? (x4 + 1/x4) (x + 1/x) = 47 x 3
    ? x5 + 1/x5 + x3 + 1/x3 = 141
    ? x5 + 1/x5 + 18 = 141 [from Eq. (iv)]
    ? x5 + 1/x5 = 123


  • Simplification problems


    Search Results


    • 1. 
      3x + 2y = 12 and xy = 6, them the value of 9x2 + 4y2 is?

    • Options
    • A. 76
    • B. 80
    • C. 72
    • D. 74
    • Discuss
    • 2. 
      (4 x 4 x 4 x 4 x 4 x 4) 5 x (4 x 4 x 4 ) 8 ÷ (4) 3 = (64) ?

    • Options
    • A. 17
    • B. 10
    • C. 16
    • D. 11
    • Discuss
    • 3. 
      If a * b = a + b + a / b, Then the value of 12 * 4 is

    • Options
    • A. 48
    • B. 19
    • C. 20
    • D. 21
    • Discuss
    • 4. 
      If a 2 + b 2 = a, then the value of a 12 + a 6 + 1 is?

    • Options
    • A. 2
    • B. 3
    • C. -3
    • D. 1
    • Discuss
    • 5. 
      (2.247) 3 + (1.730) 3 + (1.023) 3 -3 x 2.247 x 1.730 x 1.023 / [(2.247) 2 + (1.730) 2 + (1.023) 2 - 2.247 x 1.730 - 1.730 x 1.023 - 2.247 x 1.023] =?

    • Options
    • A. 1.730
    • B. 4
    • C. 5
    • D. 5.247
    • Discuss
    • 6. 
      If x + 1/x = 2, then what is value of x - 1/x ?

    • Options
    • A. 0
    • B. 1
    • C. 2
    • D. -2
    • Discuss
    • 7. 
      If x + 1/x = 6, then x 4 + 1/x 4 is?

    • Options
    • A. 1152
    • B. 1154
    • C. 1148
    • D. 1150
    • Discuss
    • 8. 
      If x + y = 18 and xy = 72, what is the value of x2 + y2?

    • Options
    • A. 120
    • B. 90
    • C. 180
    • D. Cannot be determined
    • Discuss
    • 9. 
      If x + y = 1, then the value of (x3 + y3 + 3xy) is?

    • Options
    • A. -2
    • B. 1
    • C. 2
    • D. 3
    • Discuss
    • 10. 
      If p + q = 10 and pq = 5, then the numerical value if p/q + q/p will be?

    • Options
    • A. 22
    • B. 18
    • C. 16
    • D. 20
    • Discuss


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