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JEE Mains · Maths · STD 11 - 7. binomial theoram

मान लीजिए A और B क्रमशः द्विपद प्रसरण \((1+x)^{2 \mathrm{n}-1}\) में \(30^{\text {th }}\) और \(12^{\text {th }}\) पदों के गुणांक हैं। यदि \(2 \mathrm{~A}=5 \mathrm{~B}\) है, तो n = __________

  1. A 22
  2. B 20
  3. C 21
  4. D 19
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Answer & Solution

Correct Answer

(C) 21

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Detailed explanation

\begin{aligned} & \mathrm{A}={ }^{2 \mathrm{n}-1} \mathrm{C}_{29} \quad \mathrm{~B}={ }^{2 \mathrm{n}-1} \mathrm{C}_{11} \\ & 2^{2 \mathrm{n}-1} \mathrm{C}_{29}=5{ }^{2 \mathrm{n}-1} \mathrm{C}_{11} \\ & 2 \frac{(2 \mathrm{n}-1)!}{29!(2 \mathrm{n}-30)!}=5 \frac{(2…

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