Question:

If the $ (3r)^{th} \,and\, (r+2)^{th} $ terms in the binomial expansion of $ (1 + x)^{2n} $ are equal, then

Updated On: Jun 14, 2022
  • n = r
  • n = r + 1
  • n = 2 r
  • n = 2 r - 1
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The Correct Option is C

Solution and Explanation

Answer (c) n = 2 r
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Concepts Used:

Binomial Expansion Formula

The binomial expansion formula involves binomial coefficients which are of the form 

(n/k)(or) nCk and it is calculated using the formula, nCk =n! / [(n - k)! k!]. The binomial expansion formula is also known as the binomial theorem. Here are the binomial expansion formulas.

This binomial expansion formula gives the expansion of (x + y)n where 'n' is a natural number. The expansion of (x + y)n has (n + 1) terms. This formula says:

We have (x + y)n = nC0 xn + nC1 xn-1 . y + nC2 xn-2 . y2 + … + nCn yn

General Term = Tr+1 = nCr xn-r . yr

  • General Term in (1 + x)n is nCr xr
  • In the binomial expansion of (x + y)n , the rth term from end is (n – r + 2)th .