Mathematics 9709 · AS & A Level · Series

Series — practice question

For the expansion of $(1 - 4x)^6$, the coefficient of $x^2$ is 12 times the coefficient of $x^2$ in the expansion of $(2 + ax)^5$.

(main)[3]

Determine the value of the positive constant $a$.

Worked solution & mark scheme

This 3-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Correct term $240x^2$ or $80a^2x^2$ identified” …