**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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