Find the partial sum of the first 100 terms of the series 4,8,12,16.

Hello:

16-12=12-8=8-4=4 ... (common diff by arithmetic sequence)

a1 = 4

an = a1 + (n-1) r ... r = 4

a100 = a1 + (100-1) * 4 = 4+99*4 = 5*99 = 495

the partial sum of the first 100 terms is : S100

S100 = 100/2 (4+495) = 24950