ECZ 2018 · GCE Paper 2 · Question 2 — Sequences and Series

In a geometric progression, the third term is 29and the fourth term is 227.

(a) Simplify (7st3 / 15u3v2) × (5u3v28s3t2).[2]

Verified working — step 1

Multiply the fractions and simplify powers:

(b(i)) Find the first term and the common ratio.[3]

Verified working — step 1

Let first term = a, common ratio = r.

(b(ii)) Find the sum of the first 5 terms of the geometric progression.[2]

Verified working — step 1

Use Sn = a1-r^n1-rfor r<1, n=5:

(b(iii)) Find the sum to infinity.[2]

Verified working — step 1

Since |r|<1, use S∞ = …

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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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