SPM 2017 Add Maths Paper 1, Question 9Functions

Solved on video in English and Bahasa Melayu · 3 marks · Form 4, Functions · 6:02 video

The question

Diagram 5 shows the graph of the function f: x -> |1 - 2x| for the domain -2 <= x <= 4. State (a) the object of 7, (b) the image of 3, (c) the domain of 0 <= f(x) <= 5.

[3 marks]

SPM 2017 Add Maths Paper 1, Question 9: the question as drawn in Eduly's video6:02

Step 1

Solve f(x) = 7: |1 - 2x| = 7, so 1 - 2x = 7 or 1 - 2x = -7, giving x = -3 or x = 4. Since the domain is -2 <= x <= 4, x = -3 is rejected, so the object of 7 is x = 4.

Why this step

A modulus equation gives two answers, but f only exists on −2 ≤ x ≤ 4. Test each one: x = −3 is outside, so reject it.

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

Final answer

(a) 4, (b) 5, (c) −2 ≤ x ≤ 3

Where students lose marks

Watch out: check answers against the domain −2 ≤ x ≤ 4. Reject x = −3, keep only x = 4.

Watch every step of this question solved on video (6:02), with the reason behind each step and a box that checks your own answer.

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