Arithmetic Progression

Asked by  | 19th Sep, 2008, 02:40: PM

Expert Answer:

let no. of terms be n and c.d.= d

S = n/2(a+l)  and l = a+(n-1)d   => l-a = (n-1)d

d =( l2-a2) / ( k- (l+a) ) = (l-a) (l+a) / ( k- (l+a) )= (n-1)d (l+a) / ( k- (l+a) )

k- (l+a) = (n-1) (l+a) 

k = n(l+a)  =2S

Answered by  | 19th Sep, 2008, 11:39: PM

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