Mathematics 9709 · AS & A Level · Series

Series — practice question

The second term in a geometric progression is $16$, and the sum to infinity is $100$.
(a)[4]

Find the two possible values for the first term.

(b)[4]

Show that the $n$th term of one of the two possible geometric progressions is equal to $4^{n-2}$ times the $n$th term of the other geometric progression.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “From $ar=16$ and $\frac{a}{1-r}=100$” …

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