Question:
In the expansion \({\left( {8{a^2} – \frac{1}{2}b} \right)^6}\), the coefficient of the term contains \({a^9}{ b^3}\) is:
Reference explanation:
Correct answer:
The general term in the above expansion is
\({T_{k + 1}} = {\left( { – 1} \right)^k}C_6^k{.8^{6 – k}}{a^{12 – 2k}}{.2 ^{ – k}}{b^k}\).
Ask the problem to occur when k = 3 .
Then the coefficient of the term containing \({a^9}{b^3}\) is: \( – 1280{a^9}. {b^3}\).
ADSENSE
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