SOLUTION: find the summation notation of 7+14+28+....+896

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Question 142222: find the summation notation of
7+14+28+....+896
Found 2 solutions by Edwin McCravy, jma:
Answer by Edwin McCravy(20060)   (Show Source): You can put this solution on YOUR website!

Find the summation notation of 
7 + 14 + 28 + ... + 896

Here a1 = 7, an = 896

Since 14-7 = 7 and 28-14 = 7, then d=7

an = a1 + (n-1)d

896 = 7 + (n-1)(7)
896 = 7 + 7(n-1)
896 = 7 + 7n - 7
896 = 7n
128 = n

Now we use the sum formula:

Sn = (a1 + an}

S128 = (a1 + a128}

S128 = (7 + 896)

S128 = 64(903)

S128 = 57792

Edwin
Answer by jma(1)   (Show Source): You can put this solution on YOUR website!
7+14+28+56+112+224+448+896
=
=
=7*255
=1785
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