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Sequence problem

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Sequence problem

by phoenix9801 » Thu Dec 23, 2010 1:34 am
Quick question please i need some help. Thanks


If S sub 7 =5, S sub 8 =6, what is S sub 9 ????


I know this is a linear sequence which has an equation ( S sub n= Kn+ X ) where k is a constant difference between successive terms and x is some other constant.


I want to know how did they the first four terms of a sequence are 16, 20, 24, 28 in that order ?????




Please explain in detail and the most understanding way.
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by Geva@EconomistGMAT » Thu Dec 23, 2010 3:46 am
phoenix9801 wrote:Quick question please i need some help. Thanks


If S sub 7 =5, S sub 8 =6, what is S sub 9 ????


I know this is a linear sequence which has an equation ( S sub n= Kn+ X ) where k is a constant difference between successive terms and x is some other constant.


I want to know how did they the first four terms of a sequence are 16, 20, 24, 28 in that order ?????




Please explain in detail and the most understanding way.
Ok, usually these are picked up and answered swiftly by SOMEONE, so I guess the other experts/members are holding off because they're also laboring under the same misunderstanding: what does "sub" mean in this calculation?
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by N:Dure » Thu Dec 23, 2010 4:06 am
I think he means below it as in subscript

In which case, s9 is 7?
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by phoenix9801 » Sat Jan 01, 2011 5:03 pm
N:Dure wrote:I think he means below it as in subscript

In which case, s9 is 7?


Yes I meant to Say Subscript.

Quick question please i need some help. Thanks


If S subscript 7 =5 and S subscript 8 =6, what is S subscript 9 ????


I know this is a linear sequence which has an equation ( S sub n= Kn+ X ) where k is a constant difference between successive terms and x is some other constant.


I want to know how did they the first four terms of a sequence are 16, 20, 24, 28 in that order ?????




Please explain in detail and the most understanding way.
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by Geva@EconomistGMAT » Sat Jan 01, 2011 10:54 pm
phoenix9801 wrote:
N:Dure wrote:I think he means below it as in subscript

In which case, s9 is 7?


Yes I meant to Say Subscript.

Quick question please i need some help. Thanks


If S subscript 7 =5 and S subscript 8 =6, what is S subscript 9 ????


I know this is a linear sequence which has an equation ( S sub n= Kn+ X ) where k is a constant difference between successive terms and x is some other constant.


I want to know how did they the first four terms of a sequence are 16, 20, 24, 28 in that order ?????




Please explain in detail and the most understanding way.
I must admit that I have absolutely no idea what you mean. From the information above i.e. the 7th term is 5 and the 8th term term is 6, I cannot see why the first four terms as 16, 20, 24, 28: the set 16, 20, 24, 28, ??, 5, 6 has no RULE that I see. Are you sure you have the right question / explanation? What's the source? Anything else said i the question/explanation to help clarify?
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