Higher June 2023 Paper 2 Q15
15 Expand \(\quad (x^2 - 9xy)(2x + 5y)\) [2 marks]
| Answer | Mark | Comments |
|---|---|---|
| \(2x^3 - 18x^2y + 5x^2y - 45xy^2\) | M1 | exactly 4 terms with 3 correct terms in any order may be seen in a grid implied by \(2x^3 - 13x^2y\) with one other term or \(-13x^2y - 45xy^2\) with one other term |
| \(2x^3 - 18x^2y + 5x^2y - 45xy^2\) or \(2x^3 - 13x^2y - 45xy^2\) | A1 | terms in any order do not allow if only seen in a grid |
Additional guidance
| A correct term includes the sign (in a grid allow eg \(5x^2y\) for \(+\,5x^2y\)) | |
| Condone four correct terms followed by incorrect simplification of \(x^2y\) terms, otherwise do not allow further incorrect work eg1 \(2x^3 - 18x^2y + 5x^2y - 45xy^2 = 2x^3 + 13x^2y - 45xy^2\) eg2 \(2x^3 - 18x^2y + 5x^2y - 45xy^2 = 36x^5y + 5x^2y - 45xy^2\) | M1A1 M1A0 |
| Allow equivalent fully simplified terms eg \(5x^2y\) may be seen as \(5yx^2\) | |
| For M1 allow coefficients to be incorrectly positioned eg \(x^32 - 18x^2y + y5x^2 - 45xy^2\) | M1A0 |
| \(2x^3 + -18x^2y + 5x^2y + -45xy^2\) has 4 correct terms but needs further simplification to score A1 | M1A0 |
| Terms must be processed eg do not allow \(x^2 \times 2x\) for \(2x^3\) |