Mathematics 9709 · AS & A Level · Series

Series — practice question

(main)[4]

In the expansion of $(x + 2k)^7$, where $k$ is a non-zero constant, the coefficients of $x^4$ and $x^5$ are the same. Find the value of $k$.

Worked solution & mark scheme

This 4-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Shows the $x^5$ term as $21\times 4k^2=84k^2$” …