tolong bantu aku kak plis besok dikumpulkan
= 390
Pembahasan :
1/2 + (1/3+2/3)+(1/4+2/4+3/4)+.....+(1/40+2/40+3/40+...+38/40+39/40) =
1/2 + 1 + 1 1/2 + 2 + .....
deret aritmatika.
a = 1/2
b = 1/2
n = 39
Sn = n/2 (2a + (n-1)b)
S39 =39/2 (2(1/2) + (39-1)(1/2))
= 390
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