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Rainbow_Dash
 3 years ago
Find S_n for the given arithmetic series.
a _1= 10, d = –9, n = 15
Rainbow_Dash
 3 years ago
Find S_n for the given arithmetic series. a _1= 10, d = –9, n = 15

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micahwood50
 3 years ago
Best ResponseYou've already chosen the best response.1And what does d represent?

Callisto
 3 years ago
Best ResponseYou've already chosen the best response.2Formula to use: \[S_{n}=a_n + (n1)d\]

Rainbow_Dash
 3 years ago
Best ResponseYou've already chosen the best response.0is that first one a_1 or a_n

Callisto
 3 years ago
Best ResponseYou've already chosen the best response.2I must be crazy somehow. Just a minute. Forget the previous post first!!

Callisto
 3 years ago
Best ResponseYou've already chosen the best response.2Here it goes. \[S_{n} = \frac{n}{2} [2a + (n1)d]\] a = first term, d=common difference , n=number of terms

Rainbow_Dash
 3 years ago
Best ResponseYou've already chosen the best response.0do'nt ask why but the question changed, and now i just need to write an equation.

Callisto
 3 years ago
Best ResponseYou've already chosen the best response.2Sorry for my silly mistakes :( I suppose the first one I wrote was for \(a_n\). but still, it's wrong! \(a_n=a_1+(n1)d\)

Rainbow_Dash
 3 years ago
Best ResponseYou've already chosen the best response.0thank you for your help :) this newest one is to find a_n, and once i have a_n i use the 2nd one you put?
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