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Binomial Theorem · Question 4

JEE Main 2026 (Online) 5th April Morning ShiftNumericalMedium📈 Topic in 23% papers+4
1

If the sum of the coefficients of x7 and x14 in the expansion of ( 1x3-x4 )n, x 0, is zero, then the value of n is .

Answer

21

Solution

Tr+1=nCr (x-3 )n-r (-x4 )r=(-1)r nCr x7r-3n

Let x7 come from Tr+1: 7r-3n=7; then x14 comes from Tr+2 (power rises by 7)

Sum of coefficients =(-1)r nCr+(-1)r+1 nCr+1=0

nCr=nCr+1 r+(r+1)=n n=2r+1

7r-3(2r+1)=7 r=10, n=21

Answer: 21

JEE Main 2026 (Online) 5th April Morning Shift

Keep practising — Binomial Theorem

2

The coefficient of x2 in the expansion of (2x2+ 1x )10, x 0, is :

  1. 3240
  2. 3360
  3. 3480
  4. 3600
JEE Main 2026 (Online) 5th April Evening Shift
3

Let the smallest value of k N, for which the coefficient of x3 in (1+x)3+(1+x)4+(1+x)5+ +(1+x)99+(1+kx)100, x 0, is (43n+ 1014 ) (100C3 ) for some n N, be p. Then the value of p+n is :

  1. 10
  2. 11
  3. 12
  4. 13
JEE Main 2026 (Online) 4th April Morning Shift
4

In the expansion of (9x- 13 x )18, x>0, if the term independent of x is (221)k, then k is equal to :

  1. 84
  2. 78
  3. 168
  4. 198
JEE Main 2026 (Online) 4th April Evening Shift
5

The number of elements in the set S= \(r,k) : k Z and 36Cr+1= 6 (35Cr ) (k2-3 ) \, is :

  1. 2
  2. 4
  3. 8
  4. 16
JEE Main 2026 (Online) 2nd April Morning Shift
6

If for 3 r 30, (30C30-r )+3 (30C31-r )+3 (30C32-r )+ (30C33-r )=mCr, then m equals :

  1. 31
  2. 32
  3. 33
  4. 34
JEE Main 2026 (Online) 2nd April Evening Shift
7

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

  1. Statement I is false but Statement II is true
  2. Both Statement I and Statement II are false
  3. Both Statement I and Statement II are true
  4. Statement I is true but Statement II is false
JEE Main 2026 (Online) 28th January Evening Shift
8

The sum of the coefficients of x499 and x500 in (1 + x)1000 + x(1 + x)999 + x2(1 + x)998 + + x1000 is :

  1. 1002C501
  2. 1001C501
  3. 1000C501
  4. 1002C500
JEE Main 2026 (Online) 28th January Evening Shift
9

Let S = 125! + 13! 23! + 15! 21! + up to 13 terms. If 13 S = 2kn!, k N, then n + k is equal to

  1. 50
  2. 52
  3. 49
  4. 51
JEE Main 2026 (Online) 24th January Morning Shift
10

The sum of all possible values of n N, so that the coefficients of x, x2 and x3 in the expansion of (1 + x2)2(1 + x)n, are in arithmetic progression is :

  1. 12
  2. 9
  3. 3
  4. 7
JEE Main 2026 (Online) 23rd January Morning Shift
11

The value of 100C5051 + 100C5152 + + 100C100101 is:

  1. 2101101
  2. 2100101
  3. 2100100
  4. 2101100
JEE Main 2026 (Online) 23rd January Morning Shift

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