SPM 2018 Add Maths Paper 1, Question 10Coordinate Geometry

Solved on video in English and Bahasa Melayu · 3 marks · Form 4, Coordinate Geometry · 4:23 video

The question

The following information refers to the equation of two straight lines, AB and CD. AB: y - 2kx - 3 = 0. CD: x/(3h) + y/4 = 1, where h and k are constants. Given the straight lines AB and CD are perpendicular to each other, express h in terms of k.

[3 marks]

SPM 2018 Add Maths Paper 1, Question 10: the question as drawn in Eduly's video4:23

Step 1

Rearrange AB into gradient form y = mx + c: y - 2kx - 3 = 0 gives y = 2kx + 3, so the gradient of AB is m_AB = 2k.

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

Final answer

h = 8k/3

Where students lose marks

Watch out: convert CD to gradient form first, and keep its minus sign: m_CD = −4/(3h). Perpendicular gradients multiply to −1.

Watch every step of this question solved on video (4:23), with the reason behind each step and a box that checks your own answer.

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