Home
Class 14
MATHS
Let n > 1, be a positive integer. Then t...

Let `n > 1`, be a positive integer. Then the largest integer m, such that `(n^m + 1)` divides `(1 + n + n^2 + n^3 + …..+ n^(127))` is:

A

a. 127

B

b. 63

C

c. 64

D

d. 32

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to find the largest integer \( m \) such that \( n^m + 1 \) divides the sum \( 1 + n + n^2 + n^3 + \ldots + n^{127} \). ### Step-by-Step Solution: 1. **Identify the Sum**: The expression \( 1 + n + n^2 + n^3 + \ldots + n^{127} \) is a geometric series. The formula for the sum of a geometric series is given by: \[ S = \frac{a(r^n - 1)}{r - 1} \] where \( a \) is the first term, \( r \) is the common ratio, and \( n \) is the number of terms. Here, \( a = 1 \), \( r = n \), and there are \( 128 \) terms (from \( n^0 \) to \( n^{127} \)). Thus, we can write: \[ S = \frac{1(n^{128} - 1)}{n - 1} = \frac{n^{128} - 1}{n - 1} \] 2. **Factor the Numerator**: We can factor \( n^{128} - 1 \) using the difference of squares: \[ n^{128} - 1 = (n^{64} - 1)(n^{64} + 1) \] Continuing to factor \( n^{64} - 1 \): \[ n^{64} - 1 = (n^{32} - 1)(n^{32} + 1) \] and so on, until we reach: \[ n^{128} - 1 = (n - 1)(n + 1)(n^2 + 1)(n^4 + 1)(n^8 + 1)(n^{16} + 1)(n^{32} + 1)(n^{64} + 1) \] 3. **Divisibility by \( n^m + 1 \)**: We need to check which factors of \( n^{128} - 1 \) can be expressed in the form \( n^m + 1 \). The factor \( n^{64} + 1 \) is of the form \( n^m + 1 \) where \( m = 64 \). 4. **Determine the Largest \( m \)**: To find the largest \( m \) such that \( n^m + 1 \) divides \( n^{128} - 1 \), we observe that: - \( n^1 + 1 \) divides \( n^{128} - 1 \) - \( n^2 + 1 \) divides \( n^{128} - 1 \) - \( n^4 + 1 \) divides \( n^{128} - 1 \) - \( n^8 + 1 \) divides \( n^{128} - 1 \) - \( n^{16} + 1 \) divides \( n^{128} - 1 \) - \( n^{32} + 1 \) divides \( n^{128} - 1 \) - \( n^{64} + 1 \) divides \( n^{128} - 1 \) The largest \( m \) for which \( n^m + 1 \) divides \( n^{128} - 1 \) is therefore \( m = 64 \). ### Conclusion: The largest integer \( m \) such that \( n^m + 1 \) divides \( 1 + n + n^2 + n^3 + \ldots + n^{127} \) is: \[ \boxed{64} \]
Promotional Banner

Topper's Solved these Questions

  • FUNDAMENTALS

    ARIHANT SSC|Exercise TEST OF YOU - LEARNING - 1|40 Videos
  • FUNDAMENTALS

    ARIHANT SSC|Exercise TEST OF YOU - LEARNING - 2|40 Videos
  • FUNDAMENTALS

    ARIHANT SSC|Exercise LEVEL 2|123 Videos
  • FUNCTIONS AND GRAPH

    ARIHANT SSC|Exercise Final Round|40 Videos
  • GEOMETRY

    ARIHANT SSC|Exercise EXERCISE(LEVEL 2)|52 Videos

Similar Questions

Explore conceptually related problems

The largest integer n for which n+5 divides n^(5)+5 is:

If m and n are any two odd positive integers with n

The largest value of the positive integer k for which n^(k)+1 divides 1+n+n^(2)+ . . . .+n^(127) , is

If m,n are the positive integers (n gt 1) such that m^n = 121 , then value of (m-1)^(n +1) is :

ARIHANT SSC-FUNDAMENTALS -FINAL ROUND
  1. A fruit basket contains 4 oranges, 5 apples and 6 mangoes. The number ...

    Text Solution

    |

  2. If n in 1,3,5,7,… etc., then the value of 19^(n) - 23^n - 43^n + 47^n ...

    Text Solution

    |

  3. The sum of the following series: 1.1^2 (1 - 0/1) + 2.2^(2) (1 - 1/2)...

    Text Solution

    |

  4. The distace between the houses of Sarvesh and Ravi is 900 km and the h...

    Text Solution

    |

  5. The highest power of 17 which can divide exactly the following express...

    Text Solution

    |

  6. "Help India Foundation" and "People for People Organisation" decided t...

    Text Solution

    |

  7. "Help India Foundation" and "People for People Organization" decided t...

    Text Solution

    |

  8. The number of three-digit numbers having only two consecutive digits i...

    Text Solution

    |

  9. The expression, for p != 1, (1 + p^(256)) xx (1 + p^(128)) xx (1+ p^(6...

    Text Solution

    |

  10. For the given fixed perimeter of 50 cm, the total number of rectangles...

    Text Solution

    |

  11. The total number of factors of a number is 24 and the product of the p...

    Text Solution

    |

  12. Two numbers are in the ratio 4 : 5. If each number is increased by 8, ...

    Text Solution

    |

  13. Mr. Oberaiappered in CAT for four consecutive years, but coincidently ...

    Text Solution

    |

  14. A thief somehow managed to steal some golden coins from a bank's cash ...

    Text Solution

    |

  15. The number log2 7 is :

    Text Solution

    |

  16. The product of n positive numbers is unity. Then their sum is:

    Text Solution

    |

  17. Let n > 1, be a positive integer. Then the largest integer m, such tha...

    Text Solution

    |

  18. Number of divisors of the form 4n + 2, n ge 0 which can divide 240 is ...

    Text Solution

    |

  19. If the integers m and n are chosen at random between 1 and 100, then a...

    Text Solution

    |

  20. If a ,b ,c ,d are positive real umbers such that a=b+c+d=2,t h e nM=(a...

    Text Solution

    |