ECZ 2018 · O-Level Paper 2 · Question 5 — Sequences and Series
The first three terms of a geometric progression are k + 4, k and 2k - 15 where k is a positive constant.
(a) Simplify b - aa^2 - b^2.[2]
Verified working — step 1
a2 - b2 = (a - b)(a + b) and b - a = …(b(i)) The first three terms of a geometric progression are k + 4, k and 2k - 15, where k is a positive constant. Find k.[3]
Verified working — step 1
The common ratio is the same: kk + 4= 2k - 15k(b(ii)) List the first three terms of the progression.[2]
Verified working — step 1
With k = 12: k + 4 = 16, k = 12 and 2k - 15 = …(b(iii)) Calculate the sum to infinity.[2]
Verified working — step 1
r = 1216= …The full step-by-step working and final answer are included with Premium — checked against ECZ marking standards.
Original examination question © Examinations Council of Zambia. Worked solution and commentary © G12 Titan — not to be reproduced without permission.
Have a different question?
Search it — if it is from a past paper or a school mock, chances are we have it worked out, or one that uses the same method.
Search any past-paper question