The coefficients of three consecutive terms in the expansion of(1+x)n are in the ratio 1:7:42. find  n. 

55 

  • -3

Let 1st,2nd and 3rd terms be in the ratio 1:7:42

Therefore,

nC1 x = 7

or, nx = 7  ---------------------- I

nC2 x = 42

or, n(n-1) x2 = 42

or, nx(n-1)x = 42

or, 7(n-1)x = 42

or, 7nx - 7x = 42

or, 49 - 7x = 42

or, x = 1

putting value of x in 1st equation , n = 7

Hence n = 7

 

tHuMpS uP pLeAsE ! 

  • -13

forgot to make it in powers pls understand that way. the second equation is nC2 x2

  • -6
the  coeffivicent of three consecutive terms in the expansion of (1+n) nare in the ratio 1:7:42. find n
  • -5
all are wrong..
  • -11
the answer to this question is very simple all u have to do is just solve
  • -1
But answer is 55
  • -1
This is the correct answer after you find the coefficients using the general formula. to find coefficients use general formula in Tr+1, T(r+1)+1 and T (r+2)+1.

  • 48

1 Answer

 

  • -1
I know answer
  • -1
I have share the answer
  • 2
Please find this answer

  • 0
Hsggw
  • 1
Ccccc
  • 0
This is the correct answer after you find the coefficients using the general formula. to find coefficients use general formula in Tr+1, T(r+1)+1 and T (r+2)+1.

  • 1
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