(a)[5]
Find values for $a$ and $b$.
(b)[3]
Find the total of the first 20 terms of the arithmetic progression.
Mathematics 9709 · AS & A Level · Series
Series — practice question
In an arithmetic progression, the first, second and third terms are $a$, $\frac{3}{2}a$ and $b$ respectively, where $a$ and $b$ are positive constants. In a geometric progression, the first, second and third terms are $a$, $18$ and $b + 3$ respectively.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Using $a+b=2\times 2^{\frac{3}{2}}$ correctly gives $b=2a$” …
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