SPM 2018 Add Maths Paper 1, Question 5
Solved on video in English and Bahasa Melayu · 3 marks · 4:27 video
The question
Find the value of (a) lim_{x -> 1} (7 - x², (b) f''(2) if f'(x) = 2x³ - 4x + 3.
[3 marks]
4:27Step 1
The expression 7 - x² is a polynomial, which is continuous everywhere, so the limit as x -> 1 can be found by direct substitution of x = 1.
Why this step
A polynomial has no gaps or breaks, so the limit is just its value at x = 1. You don't need factoring or other limit tricks here.
4 more steps, each with the reason for it, in the full solution
Final answer
(a) 6, (b) 20
Where students lose marks
Watch out: for (a) just substitute x = 1; for (b) differentiate the given f'(x) once more, not f(x), and don't square f'(2).
Watch every step of this question solved on video (4:27), 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.
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