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TS EAMCET · Maths · Binomial Theorem

If the 9 th and 10th terms are the numerically greatest terms in the expansion of \((5 x-6 y)^n\) when \(x=2 / 5\) and \(y=1 / 2\), then the absolute value of the middle terms of that expansion is

  1. A \(14 C_8 6^7\)
  2. B \(14 C_7 6^7\)
  3. C \(15 C_7 6^7\)
  4. D \(15 C_8 6^8\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(14 C_7 6^7\)

Step-by-step Solution

Detailed explanation

Given, 9th and 10th terms are numerically greatest terms in the expansion of \((5 x-6 y)^n\) \(9 \leq \frac{(n+1)\left(\frac{6 y}{5 x}\right)}{1+\left(\frac{6 y}{5 x}\right)}\) Here, \(y=\frac{1}{2}\) and \(x=\frac{2}{5}\)…