JEE Mains · Maths · STD 11 - 7. binomial theoram
If the coefficients of \(x^7\) in \(\left( ax ^2+\frac{1}{2 bx }\right)^{11}\) and \(x ^{-7}\) in \(\left(a x-\frac{1}{3 b x^2}\right)^{11}\) are equal, then
- A \(64 ab =243\)
- B \(729 ab =32\)
- C \(243 ab =64\)
- D \(32 ab =729\)
Answer & Solution
Correct Answer
(B) \(729 ab =32\)
Step-by-step Solution
Detailed explanation
\(\left(a x^2+\frac{1}{2 b x}\right)^{11}\) \(T _{ r +1}={ }^{11} C _{ r }\left( ax ^2\right)^{11- r } \cdot\left(\frac{1}{2 bx }\right)^{ r }\)…
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