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

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