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505-555 (Easy)|   Sequences|      
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Bunuel
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A sequence of numbers is given by the rule an = (an – 1)^2. What is a5 29 Oct 2017, 01:56
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81% (00:55) correct 19% (01:05) wrong based on 143 sessions

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A sequence of numbers is given by the rule \(a_n = (a_{n – 1})^2\). What is \(a_5\)?

(1) \(a_1 = –1\)
(2) \(a_3 = 1\)
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D
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chetan2u
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A sequence of numbers is given by the rule an = (an – 1)^2. What is a5 29 Oct 2017, 04:36
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Bunuel
A sequence of numbers is given by the rule \(a_n = (a_{n – 1})^2\). What is \(a_5\)?

(1) \(a_1 = –1\)
(2) \(a_3 = 1\)
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\(a_n = (a_{n – 1})^2\) tells us that each term is linked to another term..
so knowing ANY number in the sequence can give us the value of ALL terms in the sequence ..

we are looking for \(a_5\), so knowing any other term will help us in knowing it...

Both statements give us one value of a term, so EACH statement is sufficient

D
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A sequence of numbers is given by the rule an = (an – 1)^2. What is a5 29 Oct 2017, 10:57
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Both Statements are sufficient.

If a1 is given we can calculate a2,a3,a4 and then a5.

If a3 is given, we can calculate a4 and then a5.

IMO:D
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A sequence of numbers is given by the rule an = (an – 1)^2. What is a5 08 Jul 2019, 23:59
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A sequence of numbers is given by the rule an=(an–1)2an=(an–1)2. What is a5?

(1) a1=–1
(2) a3=1
----------
We are given how the sequence is distributed, and now we need to find out the value of the 5th term
ST1: We have the value of the 1st term, so we can easily find the value of the 2nd term and the following terms till 5th term--->Sufficient
ST2: We know the value of the 3rd term, also how the sequence is distributed, so we can easily find the 5th term--->Sufficient.
----->The answer is D
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A sequence of numbers is given by the rule an = (an – 1)^2. What is a5 09 Jul 2019, 02:25
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Bunuel
A sequence of numbers is given by the rule \(a_n = (a_{n – 1})^2\). What is \(a_5\)?

(1) \(a_1 = –1\)
(2) \(a_3 = 1\)
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Statement 1:
\(a_1 = -1 => a_2 =1 = a_3 =a_4 =a_5 =1\) SUFFICIENT

Statement 2:
\(a_3=1=a_4=a_5=1\) SUFFICIENT

Either statement is SUFFICIENT.

IMO D
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