SOLUTION: find the sum of the first n terms of the given arithmetic series a1=-13,a7=20.8 (n=7)

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Question 40980: find the sum of the first n terms of the given arithmetic series
a1=-13,a7=20.8 (n=7)
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
find the sum of the first n terms of the given arithmetic series
a1=-13,a7=20.8 (n=7)

S(7) = (7/2)(a(1)+a(7))
S(7) = 3.5(-13+20.8)
S(7) = 3.5*7.8
S(7)= 27.3
Cheers,
stan H.