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TS EAMCET · Maths · Binomial Theorem

If the coefficient of \(r\) th, \((r+1)\) th and \((r+2)\) th terms in the expansion of \((1+x)^n\) are respectively in the ratio \(2: 4: 5\), then \((r, n)=\)

  1. A \((2,7)\)
  2. B \((3,8)\)
  3. C \((3,9)\)
  4. D \((4,9)\)
Verified Solution

Answer & Solution

Correct Answer

(B) \((3,8)\)

Step-by-step Solution

Detailed explanation

The coefficients of \(r\) th, \((r+1)\) th and \((r+2 y\) th terms in the expansion of \((1+x)^n\) are \({ }^n C_{r-1},{ }^n C_r\) and \({ }^n C_{r+1}\) respectively. It is given that,…