(a)[3]
Find the ratio $p:q$ and give your answer in its simplest form.
(b)[4]
The coefficient of $x^3$ is given as $486$. Find the values of $p$ and $q$.
Mathematics 9709 · AS & A Level · Series
Series — practice question
In the expansion of $(p+qx)^4$, the coefficient of $x$ matches the coefficient of $x^2$. The constants $p$ and $q$ are both positive.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Use binomial coefficients to pick out the matching terms, for example $4p^3q$ and $6p^2q^2$” …
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