MRSM Trial 2025 Add Maths Paper 1, Question 3Linear Law

Solved on video in English · Form 4, Linear Law · 4:29 video

The question

(a)

Diagram 2 shows a straight-line graph of y√x against x. The line passes through the points (20, 2) and (6, −3/2).

(a) Based on Diagram 2, express y in terms of x.

(b)

Diagram 2 shows a straight-line graph of y√x against x, passing through (20, 2) and (6, −3/2).

(b) Find the value of y when x = 2.4.

Step 1

Treat the graph as a straight line Y = mX + c with Y = y√x and X = x, so y√x = mx + c.

Why this step

The vertical axis is y√x, not y. So we treat y√x as Y and x as X, and then Y = mX + c fits the line.

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

Final answer

y = (1/4)√x − 3/√x

Where students lose marks

Watch out: divide the whole equation by √x so y stands alone, and mind the sign of −3/2 in the gradient.

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

Final answer

y = −1.549

Where students lose marks

Watch out: x = 2.4 in y√x = (1/4)x − 3 gives y√x, not y. Divide by √x, and don't round √2.4 too early.

Watch every step of this question solved on video (4:29), with the reason behind each step and a box that checks your own answer.

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