The coefficient of $$$\frac{1}{x}$$$ in the expansion of $$$\left(2 x+\frac{a}{x^{2}}\right)^{5}$$$ is 720 . Hence find the coefficient of $$$\frac{1}{x^{7}}$$$ in the expansion. ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................

Mathematics

IGCSE&ALevel

CAIE

Exam No：9709_m20_qp_12 Year：2020 Question No：6(b)

Answer:

\[
5 \mathrm{C} 4[2(x)]\left[\frac{\text { their } a}{\left(x^{2}\right)}\right]^{4}
\]
810 identified

Knowledge points:

1.6.1 use the expansion of , where is a positive integer (Including the notations and n!) (Knowledge of the greatest term and properties of the coefficients are not required.)

Answer:

Knowledge points:

Solution:

Related Question