Higher June 2025 Paper 2 Q20
20 David has solved the inequality \(\quad x^2 \lt 16 \quad\) and represented his solution on the number line below.
Give one reason why David’s solution is wrong. [1 mark]
| Answer | Mark | Comments |
|---|---|---|
| Correct reason indicating that the circles should be unshaded or \((x =)\ 4\) is not a solution or \((x =)\ -4\) is not a solution | B1 | eg the circles should be white or \((x =)\ 4\) doesn’t satisfy \(x^2 \lt 16\) |
Additional guidance
| Ignore non-contradictory statements alongside a correct reason eg 4 is not a solution. Squaring a number is always \(\geqslant 0\) | B1 |
| Incorrect statement with a correct reason is choice eg Circles should be white and should be at \(-3\) and 3 | B0 |
| Condone \(-4^2\) if recovered to 16 | |
| Circles should be blank | B1 |
| Circles crossed out and replaced with open circles above \(-4\) and 4 | B1 |
| \(-4^2\) is 16 so \(-4\) shouldn’t be a solution | B1 |
| One circle should be white | B0 |
| Coloured dot means equal to | B0 |
| The circles are the wrong colour | B0 |
| Both circles are black so he is doing \(x\) squared is 16 | B0 |
| 4 squared is 16 | B0 |
| His solution is \(-4 \leqslant x \leqslant 4\) | B0 |