SPM 2019 Add Maths Paper 1, Question 7Progressions

Solved on video in English and Bahasa Melayu · 3 marks · Form 4, Progressions · 3:45 video

The question

Three consecutive terms of a geometric progression are 32, p, q. It is given that the sum of these three terms is 26. Find the possible values of p and of q.

[3 marks]

SPM 2019 Add Maths Paper 1, Question 7: the question as drawn in Eduly's video3:45

Step 1

Since 32, p, q are consecutive GP terms, the common ratio satisfies p/32 = q/p, so p² = 32q, i.e. q = p²/32.

Why this step

In a GP, every term is the previous one times the same ratio. So p/32 equals q/p, and that links p and q in one equation.

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

Final answer

p = −8, q = 2 or p = −24, q = 18

Where students lose marks

Watch out: the quadratic gives two values of p, so give both pairs and match each q to its own p.

Watch every step of this question solved on video (3:45), with the reason behind each step and a box that checks your own answer.

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