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If 35cn +7 = 35c4n − 2 , Then Write the Values of N. - Mathematics

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Question

If 35Cn +7 = 35C4n − 2 , then write the values of n.

Solution

 35Cn +7 = 35C4n − 2 

\[n + 7 + 4n - 2 = 35\]   [∵\[{}^n C_x =^n C_y \Rightarrow n = x + y\ \text{or} x = y\]]
\[\Rightarrow 5n = 30\]
\[ \Rightarrow n = 6\]
\[\text{And}, n + 7 = 4n - 2\]
\[ \Rightarrow n = 3\]
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Factorial N (N!) Permutations and Combinations
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Chapter 17: Combinations - Exercise 17.4 [Page 24]

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RD Sharma Mathematics [English] Class 11
Chapter 17 Combinations
Exercise 17.4 | Q 2 | Page 24

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