Date | May 2019 | Marks available | 9 | Reference code | 19M.1.AHL.TZ1.H_7 |
Level | Additional Higher Level | Paper | Paper 1 (without calculator) | Time zone | Time zone 1 |
Command term | Find | Question number | H_7 | Adapted from | N/A |
Question
Find the coordinates of the points on the curve y3+3xy2−x3=27 at which dydx=0.
Markscheme
* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.
attempt at implicit differentiation M1
3y2dydx+3y2+6xydydx−3x2=0 A1A1
Note: Award A1 for the second & third terms, A1 for the first term, fourth term & RHS equal to zero.
substitution of dydx=0 M1
3y2−3x2=0
⇒y=±x A1
substitute either variable into original equation M1
y=x⇒x3=9⇒x=3√9 (or y3=9⇒y=3√9) A1
y=−x⇒x3=27⇒x=3 (or y3=−27⇒y=−3) A1
(3√9,3√9) , (3, −3) A1
[9 marks]