## (Math Quiz 10 – CT) In the expansion ({left( {a – 2b} right)^8}), the coefficient of the containing term ({a^4}. {b^4}) is:

• Question:

In the expansion $${\left( {a – 2b} \right)^8}$$, the coefficient of the term containing $${a^4}.{b^4}$$ is:

Reference explanation:

The general term in the above expansion is

$${T_{k + 1}} = C_8^k. {a^{8 – k}}. {\left( { – 2} \right)^k}. {b^k}$$

Ask the problem to happen when k = 4.

Then the coefficient of the term containing $${a^4}.{b^4}$$ is: $$C_8^4{.2^4} = 1120$$.