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AP EAMCET · Maths · Binomial Theorem

If \({ }^n C_7={ }^n C_6\), then \({ }^n C_2=\)

  1. A 858
  2. B 13
  3. C 1
  4. D 78
Verified Solution

Answer & Solution

Correct Answer

(D) 78

Step-by-step Solution

Detailed explanation

\begin{aligned} & \text { Given, }{ }^n C_7={ }^n C_6 \\ & \begin{array}{l} \Rightarrow n=7+6=13\left\{\text { If }{ }^n C_x={ }^n C_y \Rightarrow \text { either } x=y\right. \text { or } \\ x+y=n\} \end{array} \\ & \therefore{ }^n C_2={ }^{13} C_2=\frac{13 \times 12}{2}=13…