SPM 2022 Add Maths Paper 1, Question 11Indices, Surds & Logarithms

Solved on video in English and Bahasa Melayu · Form 4, Indices, Surds & Logarithms · 5:35 video

The question

11 Diagram 7 shows triangle ABC. It is given that BC = (2 + x) cm, AD² = 1 + sqrt(2), and ABD is a straight line. The base AB = sqrt(x) cm and CD = (2 − x) cm, with a right angle at D. Show that x = (1 + 5·sqrt(2))/49 cm.

SPM 2022 Add Maths Paper 1, Question 11: the question as drawn in Eduly's video5:35

Step 1

In right triangle BCD (right angle at D): BC² = BD² + CD², so BD² = BC² − CD² = (2 + x)² − (2 − x)².

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

Final answer

Shown: x = (1 + 5√2)/49 cm

Where students lose marks

Watch out: don't take √ of AD² = 1 + √2. Write AD = AB + BD in terms of x, then square it.

Watch every step of this question solved on video (5:35), with the reason behind each step and a box that checks your own answer.

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