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Find the Middle Term in the Expansion Of: (Ii) ( a X + B X ) 12

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Question

Find the middle term in the expansion of: 

(ii)  \[\left( \frac{a}{x} + bx \right)^{12}\]

 

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Solution

(ii) Here,
n = 12 (Even number)
Therefore, the middle term is the 

\[\left( \frac{n}{2} + 1 \right)th\]   i.e. 7th term
 
\[Now, \]
\[ T_7 = T_{6 + 1} \]
\[ =^{12}{}{C}_6 \left( \frac{a}{x} \right)^{12 - 6} (bx )^6 \]
\[ = ^{12}{}{C}_6 a^6 b^6 \]
\[ = \frac{12 \times 11 \times 10 \times 9 \times 8 \times 7}{6 \times 5 \times 4 \times 3 \times 2} a^6 b^6 \]
\[ = 924 a^6 b^6\]

 

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Chapter 18: Binomial Theorem - Exercise 18.2 [Page 38]

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R.D. Sharma Mathematics [English] Class 11
Chapter 18 Binomial Theorem
Exercise 18.2 | Q 13.2 | Page 38

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