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/sci/ - Science & Math

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2188796 No.2188796 [Reply] [Original]

Find the sum of the arithmetic sequence

3, 9, 15,......., 75

Someone explain how to do this plox.

>> No.2188803

Find the sum of the arithmetic sequence

1, 2, 3,......, 25

then multiply by 3.

>> No.2188809
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2188809

it's plus six everytime faggot

>> No.2188813

n(n+1)/2

>> No.2188814

>>2188809

I know it's plus six every time. I don't get what is meant by the "sum" of the sequence.

>> No.2188818

x*y/2

it's a fucking triangle.

>> No.2188823

you can easily find an proof a formula for the sum of an arithmetic sequence.

Are your parents brother and sister?
Fucking idiotic American high school fucktards, too stupid to even use wikipedia..

>> No.2188825

>>2188814
Add up all the numbers in the sequence dumbass.

>> No.2188839

>>2188825

3+9+15=27

I'm pretty damn sure, this is not what you mean.

>> No.2188884
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2188884

>>2188823
>mfw your from Amurica too

>> No.2188889

>>2188884
actually I'm not.
Sonst könnte ich wohl kaum fließend deutsch sprechen, du Maco-Möbel Jude.

>> No.2188901

You are clearly 14 years old OP
Go and re-read your math textbook

>> No.2188997

75+3=78
78/3=26
There are 26 terms in this sequence.
The sum of the sequence is (78*26)/2 = 1014
Just like 1,2,3,4..9,10. Take the first and the last term and add them = 11. 11 times the number of terms, ten in this case gives 110. Divide by two and you get 55.
Same principle.
Last term + first term times number of terms, divided by two.

>> No.2189026

http://en.wikipedia.org/wiki/Arithmetic_progression

on another note, underage ban?