| Exam Board | Edexcel |
|---|---|
| Module | C1 (Core Mathematics 1) |
| Marks | 6 |
| Paper | Download PDF ↗ |
| Topic | Arithmetic Sequences and Series |
| Type | Sequence defined by formula |
| Difficulty | Easy -1.2 This is a straightforward C1 arithmetic series question requiring only direct substitution to find terms, identification of the common difference by inspection, and a standard summation proof using the formula for sum of an AP. All steps are routine with no problem-solving insight needed, making it easier than average but not trivial due to the algebraic manipulation required in part (c). |
| Spec | 1.04h Arithmetic sequences: nth term and sum formulae |
The $r$th term of an arithmetic series is $(2r - 5)$.
\begin{enumerate}[label=(\alph*)]
\item Write down the first three terms of this series. [2]
\item State the value of the common difference. [1]
\item Show that $\sum_{r=1}^n (2r - 5) = n(n - 4)$. [3]
\end{enumerate}
\hfill \mbox{\textit{Edexcel C1 Q5 [6]}}