SPM 2018 Add Maths Paper 2, Question 2Functions

Solved on video in English and Bahasa Melayu · 8 marks · Form 4, Functions · 6:52 video

The question

It is given that f : x -> 2x - 3 and g : x -> 1 - 3x. (a) Find (i) g(5), (ii) the value of m if f(m + 2) = (1/7) g(5), (iii) gf(x). (b) Hence, sketch the graph of y = |gf(x)| for -1 <= x <= 3. State the range of y.

[8 marks]

SPM 2018 Add Maths Paper 2, Question 2: the question as drawn in Eduly's video6:52

Step 1

Using g(x) = 1 - 3x: g(5) = 1 - 3(5) = 1 - 15 = -14.

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

Final answer

g(5) = −14; m = −3/2; gf(x) = 10 − 6x; range 0 ≤ y ≤ 16 (sketch: V with vertex (5/3, 0))

Where students lose marks

Watch out: gf means f first, then g. After the modulus, the maximum is 16 (at x = −1), not 8.

Watch every step of this question solved on video (6:52), with the reason behind each step and a box that checks your own answer.

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