SPM 2017 Add Maths Paper 1, Question 10Functions

Solved on video in English and Bahasa Melayu · 4 marks · Form 4, Functions · 3:58 video

The question

Given the function g: x -> 2x - 8, find (a) g⁻¹(x), (b) the value of p such that g²(3p/2) = 30.

[4 marks]

Step 1

Let y = g(x) = 2x - 8, so 2x = y + 8, giving x = (y+8)/2. Thus g⁻¹(x) = (x+8)/2.

Why this step

We solve for x to undo g. Then we write y as x, so the inverse is a rule in x, just like g(x).

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

Final answer

(a) g⁻¹(x) = (x + 8)/2, (b) p = 9

Where students lose marks

Watch out: g² means g(g(x)), not [g(x)]². Feed 2x − 8 into g again instead of squaring it.

Watch every step of this question solved on video (3:58), 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.