Mathematics 9709 · AS & A Level · Series

Series — practice question

In the expansion of $(2x + \frac{a}{x^2})^5$, the coefficient of $\frac{1}{x}$ is $720$.

(a)[3]

Find the possible values of the constant $a$.

(b)[2]

Hence find the coefficient of $\frac{1}{x^7}$ in the expansion.

Worked solution & mark scheme

This 5-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Uses the binomial expansion structure correctly” …