November 2021 Paper 2 Q9
9
(a) Circle the expression that is equivalent to \(\quad \dfrac{1}{a} + \dfrac{1}{b}\) [1 mark]
- \(\dfrac{2}{a + b}\)
- \(\dfrac{ab}{b + a}\)
- \(\dfrac{2}{ab}\)
- \(\dfrac{b + a}{ab}\)
(b) Simplify fully \(\quad \dfrac{6c^4 - c^3}{36c^2 - 1}\) [3 marks]
| Answer | Mark | Comments |
|---|---|---|
| \(\dfrac{b + a}{ab}\) | B1 |
| Answer | Mark | Comments |
|---|---|---|
| \(\dfrac{c^3}{6c + 1}\) | B3 | B2 \(c^3(6c - 1)\) and \((6c + 1)(6c - 1)\) B1 \(c^3(6c - 1)\) or \((6c + 1)(6c - 1)\) |
Additional guidance
| \(\dfrac{c^3}{6c + 1}\) followed by incorrect further work | B2 |