SPM 2019 Add Maths Paper 1, Question 17Differentiation

Solved on video in English and Bahasa Melayu · 4 marks · Form 5, Differentiation · 4:11 video

The question

The curve y = px⁴ + 2x has a turning point at (-1, q). Find the value of p and of q.

[4 marks]

SPM 2019 Add Maths Paper 1, Question 17: the question as drawn in Eduly's video4:11

Step 1

At a turning point, dy/dx = 0. Differentiate: dy/dx = 4px³ + 2.

Why this step

At a turning point the curve flattens, so the tangent is horizontal. Horizontal means gradient zero, and dy/dx measures gradient, so we set dy/dx = 0.

3 more steps, each with the reason for it, in the full solution

Final answer

p = 1/2, q = −3/2

Where students lose marks

Watch out: find q from the original curve, not the derivative, and mind signs: (−1)³ = −1 but (−1)⁴ = +1.

Watch every step of this question solved on video (4:11), with the reason behind each step and a box that checks your own answer.

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