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**soha****Real Member**- Registered: 2006-07-07
- Posts: 2,530

Try solving these:-

1) Find the sum of the

a) first 11 terms of AP 2, 6, 10...

b) first 13 terms of the AP -6, 0,6,...

c) first 51 terms of the AP whose second term is 2 and fourth term is 8.

2) Evaluate S12 for arithmetic sequence...

-9,-5,-1,3,7.......

"Let us realize that: the privilege to work is a gift, the power to work is a blessing, the love of work is success!"

- David O. McKay

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 86,776

Hi soha;

By the formula:

Where

Sn = sum to n terms

n is the number of terms

d = constant difference

s1= first term

a)

Formula:

b)

c)

s2 = 2 and s4 = 8 Add them both up and divide by 2 to get 5. This gives you a constant term of 3 (5-2 = 3 , 8 - 5 = 3)

The sequence is:

-1,2,5,8,11...

Glad to help ya!!!

*Last edited by bobbym (2009-10-11 10:08:21)*

**In mathematics, you don't understand things. You just get used to them.Of course that result can be rigorously obtained, but who cares?Combinatorics is Algebra and Algebra is Combinatorics.**

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**soha****Real Member**- Registered: 2006-07-07
- Posts: 2,530

Yippee!!!! Right!!!

"Let us realize that: the privilege to work is a gift, the power to work is a blessing, the love of work is success!"

- David O. McKay

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