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Date May 2017 Marks available 3 Reference code 17M.1.AHL.TZ1.H_7
Level Additional Higher Level Paper Paper 1 Time zone Time zone 1
Command term Determine Question number H_7 Adapted from N/A

Question

An arithmetic sequence u1u2u3u1u2u3 has u1=1u1=1 and common difference d0d0. Given that u2u3u2u3 and u6u6 are the first three terms of a geometric sequence

Given that uN=15uN=15

find the value of dd.

[4]
a.

determine the value of Nr=1urNr=1ur.

[3]
b.

Markscheme

* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.

use of un=u1+(n1)dun=u1+(n1)d     M1

(1+2d)2=(1+d)(1+5d)(1+2d)2=(1+d)(1+5d) (or equivalent)     M1A1

d=2d=2     A1

[4 marks]

a.

1+(N1)×2=151+(N1)×2=15

N=9N=9     (A1)

9r=1ur=92(2+8×2)9r=1ur=92(2+8×2)     (M1)

=63=63     A1

[3 marks]

b.

Examiners report

[N/A]
a.
[N/A]
b.

Syllabus sections

Topic 1—Number and algebra » SL 1.2—Arithmetic sequences and series
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Topic 1—Number and algebra

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