Mathematics 9709 · AS & A Level · Series

Series — practice question

(a)[3]

For an arithmetic progression with the sum of the first $n$ terms, $S_n$, given by $S_n = n^2 + 8n$, determine the first term and the common difference.

(b)[5]

In a geometric progression, the second term is $9$ less than the first term. The total of the second and third terms is $30$. If every term in the progression is positive, find the first term.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: Recognises $S_n = n^2 + 8n$

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