(a)[1]
Show that $(n - 1)d = \frac{11726}{n} - 8$ by rearranging the given expression.
(b)[4]
Since the $n$th term is $139$, determine the values of $n$ and $d$, with $d$ expressed as a fraction.
Mathematics 9709 · AS & A Level · Series
Series — practice question
An arithmetic progression starts with term $4$ and has common difference $d$. The total of its first $n$ terms is $5863$.
Worked solution & mark scheme
This 5-mark question has a full step-by-step worked solution and mark scheme. One marking point: “A useful intermediate result is $\frac{n}{2}[8+(n-1)d]=5863$, which can then be changed into $n[8+(n-1)d]=11726$” …
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