A) 9
B) 14
C) 11
D) 12
Correct Answer: B
Solution :
\[{{2.}^{n}}{{C}_{5}}{{-}^{n}}{{C}_{4}}{{+}^{n}}{{C}_{6}}\] |
\[2.\frac{\left| \!{\nderline {\, n \,}} \right. }{\left| \!{\nderline {\, 5\left| \!{\nderline {\, n-5 \,}} \right. \,}} \right. }=\frac{\left| \!{\nderline {\, n \,}} \right. }{\left| \!{\nderline {\, 4\left| \!{\nderline {\, n-4 \,}} \right. \,}} \right. }+\frac{\left| \!{\nderline {\, n \,}} \right. }{\left| \!{\nderline {\, 6\left| \!{\nderline {\, n-6 \,}} \right. \,}} \right. }\] |
\[\frac{2}{5}.\frac{1}{n-5}=\frac{1}{(n-4)(n-5)}+\frac{1}{30}\] |
\[n=14\]satisfying equation. |
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