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**4littlepiggiesmom****Member**- Registered: 2006-01-09
- Posts: 42

My daughter had to miss math class for a music event and wants me to check her answers??? So here I am looking for help~

Find the sum of the first 100 terms of the aruthmetic sequence 19, 13 ,7,.....? We came up with b

a. -58,100

b. -556

c. _27,800

d. -55,600

e. nnone of these

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**George,Y****Member**- Registered: 2006-03-12
- Posts: 1,306

c, and there is a little trick-- notice c is one half of d, and think what's in the examiner's mind to do so

**X'(y-Xβ)=0**

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**4littlepiggiesmom****Member**- Registered: 2006-01-09
- Posts: 42

Thanks!

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**Jenilia****Member**- Registered: 2005-07-09
- Posts: 64

What is a aruthmetic sequence?

Ideas are funny little things, they won't work unless you do.

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**ganesh****Moderator**- Registered: 2005-06-28
- Posts: 18,623

An Arithmetic Progression or sequence is such that the difference between any two successive terms of the series is the same. For example,

(1) 2, 5, 8, 11, 14, 17, ...

(2) 1, 5, 9, 14, 17, 21, .....

(3) 15, 13, 11, 9, 7, 5, 3, 1, ...

(4) 0.5, 2, 3.5, 5, 6.5, 8, 9.5 etc.

You can see that the difference between any two consecutive terms is always the same for the entire series. In example (1), it is 3, in (2) it is 4, in (3), it is -2 and in (4) it is 1.5.

The first erms of the Aritmetic Series or Progression is denoted by 'a' and the common difference by 'd'.

The nth term, tn is given by tn= a+(n-1)d and

the sum of n terms is given by

Sn= n/2[2a+(n-1)d]

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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