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Date May 2019 Marks available 9 Reference code 19M.1.AHL.TZ1.H_7
Level Additional Higher Level Paper Paper 1 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  y 3 + 3 x y 2 x 3 = 27 at which d y d x = 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

3 y 2 d y d x + 3 y 2 + 6 x y d y d x 3 x 2 = 0       A1A1

Note: Award A1 for the second & third terms, A1 for the first term, fourth term & RHS equal to zero.

substitution of  d y d x = 0       M1

3 y 2 3 x 2 = 0

y = ± x       A1

substitute either variable into original equation       M1

y = x x 3 = 9 x = 9 3    (or  y 3 = 9 y = 9 3 )      A1

y = x x 3 = 27 x = 3    (or   y 3 = 27 y = 3 )      A1

( 9 3 , 9 3 ) , (3, −3)      A1

[9 marks]

Examiners report

[N/A]

Syllabus sections

Topic 5—Calculus » SL 5.3—Differentiating polynomials, n E Z
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