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

If the coefficients of the middle terms in the binomial expansions of \((1 + \alpha x)^{26}\) and \((1 - \alpha x)^{28}\), \(\alpha \neq 0\), are equal, then the value of \(\alpha\) is:

  1. A \(1\)
  2. B \(\dfrac{14}{13}\)
  3. C \(\dfrac{27}{7}\)
  4. D \(\dfrac{7}{27}\)
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Answer & Solution

Correct Answer

(D) \(\dfrac{7}{27}\)

Step-by-step Solution

Detailed explanation

The expansion of \((1 + \alpha x)^{26}\) has \(27\) terms. The middle term is \(T_{14}\). The coefficient of the middle term is \(^{26}C_{13} \alpha^{13}\). The expansion of \((1 - \alpha x)^{28}\) has \(29\) terms. The middle term is \(T_{15}\). The coefficient of the middle…
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