SPM 2021 Add Maths Paper 1, Question 2Linear Law

Solved on video in English and Bahasa Melayu · Form 4, Linear Law · 4:46 video

The question

Diagram 2 shows a straight line graph of ln y against ln x. The line passes through the points (2, 1) and (5, 7). Express y in terms of x.

Step 1

Write the linear form Y = mX + c with Y = ln y and X = ln x: ln y = m ln x + c.

Why this step

The axes are ln y and ln x, so treat them as Y and X in Y = mX + c. Then gradient and intercept give the relationship.

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

Final answer

y = x²/e³

Where students lose marks

Watch out: ln y = 2 ln x − 3 is not y = x² − 3. Make the right side one ln first.

Watch every step of this question solved on video (4:46), with the reason behind each step and a box that checks your own answer.

No card. Every past-year question on video, in English and BM.