ECZ 2021 · GCE Paper 2 · Question 1 — Sequences and Series

Geometric progression 4, 2, 1, ...

(a) Simplify a^2 x^2 - b^2 y^2ax + by.[2]

Verified working — step 1

Factor the numerator as a difference of two squares:

(b(i)) Find the 7th term.[2]

Verified working — step 1

First term a = 4, common ratio r = 24= 12.

(b(ii)) Find the sum of the first 9 terms.[3]

Verified working — step 1

Sum of n terms: Sn = a1 - r^n1 - r

(c) Find the geometric mean of 196 and 15 625.[2]

Verified working — step 1

Geometric mean of two numbers x and y is √(xy).

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Original examination question © Examinations Council of Zambia. Worked solution and commentary © G12 Titan — not to be reproduced without permission.

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