Selangor Trial 2025 Add Maths Paper 2, Question 10Linear Law

Solved on video in English · Form 4, Linear Law · 5:01 video

The question

(a)

Table 1.1 shows the values of two variables, x and y, obtained from an experiment. A straight line will be obtained when a graph of xy against x² is plotted. Table 1.1: x = 1, 2, 3, 4, 5, 6; y = 12.8, 7.6, 6.6, 6.2, 6.3, 6.8. (a) Based on Table 1.1, complete Table 1.2 (values of x² and xy).

(b)

(b) Plot xy against x², using a scale of 2 cm to 5 units on the xy-axis and the x²-axis. Hence, draw the line of best fit.

(c)(i)

(c) Using the graph in (b), (i) find the value of y when x = 4.472.

(c)(ii)

(c)(ii) Express y in terms of x.

Selangor Trial 2025 Add Maths Paper 2, Question 10: the question as drawn in Eduly's video5:01

Part (a)

Step 1

Compute x² for each x: 1² = 1, 2² = 4, 3² = 9, 4² = 16, 5² = 25, 6² = 36.

Why this step

Our graph plots xy against x², so the horizontal values must be x squared, not x itself.

1 more step, with the reason for it, in the full solution

Final answer

x²: 1, 4, 9, 16, 25, 36; xy: 12.8, 15.2, 19.8, 24.8, 31.5, 40.8

Where students lose marks

Watch out: do not round xy early (keep 19.8, not 20), and multiply x by y, do not add them.

Part (b)

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

Final answer

Graph and line of best fit (see video)

Where students lose marks

Watch out: keep a uniform scale (2 cm to 5 units), plot accurately, and draw one line that balances the points.

Part (c)(i)

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

Final answer

y ≈ 6.261 (3500/559)

Where students lose marks

Watch out: read the graph at x² ≈ 20, not at x = 4.472, then divide the xy value by x to get y.

Part (c)(ii)

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

Final answer

y = 0.8x + 12/x

Where students lose marks

Watch out: divide every term by x so the answer reads y = ..., not xy = ..., and read m and c accurately.

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