Answers

2014-11-04T16:15:14+05:30
In Arithmetic progression.............An means n th term
ans Sn means sum of first 'n' terms
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2014-11-04T16:18:20+05:30
S_n is the sum of a n th terms of a a series in AP
A_n is the n th term of an AP

S_n=\frac{n}{2}[2a+(n-1)d]

A_n=a+(n-1)d

Where n = number of terms 
a = first term 
d= common difference

in a AP


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