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Question

Question: If \(2^{n}\) occurs in the \(2^{n - 1} - 1\) term in the expansion of \(C_{0},C_{1},C_{2},.......,C_...

If 2n2^{n} occurs in the 2n112^{n - 1} - 1 term in the expansion of C0,C1,C2,.......,CnC_{0},C_{1},C_{2},.......,C_{n}, then 2.C1+23.C3+25.C5+....2.C_{1} + 2^{3}.C_{3} + 2^{5}.C_{5} + ....

A

7

B

8

C

9

D

10

Answer

9

Explanation

Solution

(55+11)2n+1(5511)2n+1(5\sqrt{5} + 11)^{2n + 1} - (5\sqrt{5} - 11)^{2n + 1}

=2{2n+1C1(55)2n.11+2n+1C3(55)2n2 = 2\left\{ 2n + 1C_{1}(5\sqrt{5})^{2n}.11 +^{2n + 1}C_{3}(5\sqrt{5})^{2n - 2} \right.\ .