Mathematics 9709 · AS & A Level · Series

Series — practice question

(a)[2]

Use the binomial theorem to expand $(1 + 3x)^6$ in ascending powers of $x$, stopping at and including the term in $x^2$.

(b)[2]

Hence find the coefficient of $x^2$ in the expansion of $(1 - 7x + x^2)(1 + 3x)^6$.

Worked solution & mark scheme

This 4-mark question has a full step-by-step worked solution and mark scheme. One marking point: “The correctly expanded form is $1+18x+135x^2$” …