| Exam Board | WJEC |
|---|---|
| Module | Unit 1 (Unit 1) |
| Year | 2019 |
| Session | June |
| Marks | 3 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Proof |
| Type | Proof by exhaustion with table |
| Difficulty | Easy -1.8 This is a trivial proof by exhaustion requiring only substitution of four values (n=1,2,3,4) and checking primality of small numbers (7, 13, 23, 37). No problem-solving or mathematical insight is needed—just arithmetic verification, making it significantly easier than average A-level questions. |
| Spec | 1.01a Proof: structure of mathematical proof and logical steps |
Given that $n$ is an integer such that $1 \leq n \leq 4$, prove that $2n^2 + 5$ is a prime number. [3]
\hfill \mbox{\textit{WJEC Unit 1 2019 Q05 [3]}}