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JEE Mains · Maths · STD 11 - 7. binomial theoram

If \({\left( {2 + \frac{x}{3}} \right)^{55}}\) is expanded in the ascending powers of \(x\) and the coefficients of powers of \(x\) in two consecutive terms of the expansion are equal, then these terms are

  1. A \(8^{th}\) and \(9^{th}\)
  2. B \(7^{th}\) and \(8^{th}\)
  3. C \(28^{th}\) and \(29^{th}\)
  4. D \(27^{th}\) and \(28^{th}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(8^{th}\) and \(9^{th}\)

Step-by-step Solution

Detailed explanation

Let \((r+1)^{\text {th }}\) and \((r+2)^{\text {th }}\) term has equal coefficient \(\left(2+\frac{x}{3}\right)^{55}=2^{55}\left(1+\frac{x}{6}\right)^{55}\) \((r+1)^{\text {th }}\) term \(=2^{55\, 55} \mathrm{C}_{r}\left(\frac{x}{6}\right)^{r}\) Coefficient of \(x^{r}\) is…
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