Edexcel C2 — Question 2 5 marks

Exam BoardEdexcel
ModuleC2 (Core Mathematics 2)
Marks5
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicGeometric Sequences and Series
TypeForm and solve quadratic in parameter
DifficultyStandard +0.3 This is a straightforward C2 question requiring students to apply the constant ratio property of geometric sequences (middle term squared equals product of outer terms), leading to a simple quadratic equation. While it involves algebraic manipulation, it's a standard textbook exercise with a clear method and no conceptual subtlety, making it slightly easier than average.
Spec1.04i Geometric sequences: nth term and finite series sum

2. The first three terms of a geometric series are ( \(p - 1\) ), 2 and ( \(2 p + 5\) ) respectively, where \(p\) is a constant. Find the two possible values of \(p\).

AnswerMarks
\(\frac{2}{p-1} = \frac{2p+5}{2}\)M1
\((2p + 5)(p - 1) = 4\)M1
\(2p^2 + 3p - 9 = 0\)A1
\((2p - 3)(p + 3) = 0\)M1 A1
\(p = -3, \frac{3}{2}\)A1
$\frac{2}{p-1} = \frac{2p+5}{2}$ | M1 |
$(2p + 5)(p - 1) = 4$ | M1 |
$2p^2 + 3p - 9 = 0$ | A1 |
$(2p - 3)(p + 3) = 0$ | M1 A1 |
$p = -3, \frac{3}{2}$ | A1 |

---
2. The first three terms of a geometric series are ( $p - 1$ ), 2 and ( $2 p + 5$ ) respectively, where $p$ is a constant.

Find the two possible values of $p$.\\

\hfill \mbox{\textit{Edexcel C2  Q2 [5]}}