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# The sequence S is defined by Sn = Sn – 1 + Sn – 2 – 3 for

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GRE Prep Club Legend
Joined: 07 Jun 2014
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GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
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The sequence S is defined by Sn = Sn – 1 + Sn – 2 – 3 for [#permalink]  25 Jul 2018, 17:25
Expert's post
00:00

Question Stats:

100% (01:00) correct 0% (00:00) wrong based on 4 sessions
The sequence S is defined by $$S_n = S_{n – 1} + S_{n – 2} – 3$$ for each integer n ≥ 3. If $$S_1 = 5$$ and $$S_2 = 0$$, what is the value of $$S_6$$?

(A) –6
(B) –5
(C) –3
(D) –1
(E) 1
[Reveal] Spoiler: OA

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Sandy
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GRE Prep Club Legend
Joined: 07 Jun 2014
Posts: 4856
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 102

Kudos [?]: 1737 [0], given: 397

Re: The sequence S is defined by Sn = Sn – 1 + Sn – 2 – 3 for [#permalink]  11 Aug 2018, 16:54
Expert's post
Explanation

The sequence $$S_n = S_{n – 1} + S_{n - 2} - 3$$ can be read as “to get any term in sequence S, sum the two previous terms and subtract 3.”

The problem gives the first two terms and asks for the sixth term:

 5 0 $$S_1$$ $$S_2$$ $$S_3$$ $$S_4$$ $$S_5$$ $$S_6$$

To get any term, sum the two previous terms and subtract 3. So the third term will equal 5 + 0 – 3 = 2.

The fourth term will equal 0 + 2 – 3 = –1. The fifth term will equal 2 + (–1) – 3 = –2. The sixth term will equal –1 + (–2) – 3 = –6:

 5 0 2 -1 -2 -6 $$S_1$$ $$S_2$$ $$S_3$$ $$S_4$$ $$S_5$$ $$S_6$$

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Sandy
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Re: The sequence S is defined by Sn = Sn – 1 + Sn – 2 – 3 for   [#permalink] 11 Aug 2018, 16:54
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