1/2+2/5+1/3+2/7+1/4+2/9+1/5 tentukan notasi sigma pake cara ya kak contoh U1,U2,U3,U4

Notasi SIgma

1/2 + 2/5 + 1/3 + 2/7 + 1/4 + 2/9 + 1/5
.
uraikan
(1/2 + 1/3 + 1/4 + 1/5) + (2/5 + 2/7 + 2/9)

untuk  (1/2 + 1/3 + 1/4 + 1/5)
n = 1 --> u1 = 1/2 = 1/(1+1)
n= 2 --> u2 = 1/3 = 1/(2+1)
n = 3 --> u3 = 1/4 = 1/(3+1)
n = 4 --> u4 = 1/5 = 1/(4+1)
.
Un = 1/(n+1)
Notasi sigma
4
∑  1/(n+1)
n= 1



untuk 2/5 + 2/7 + 2/9
n= 1 --> u1 = 2/5
n =2 --> u2 = 2/7
n = 3 --> u3 = 2/9
perhatikan penyebut nya berubah 5,7,9
a= 5, b = 2 -->  2n + 3
Un = 2/(2n +3)
notasi sigma
3
∑ 2/(2n +3)
n = 1
.
gabungkan
4...................3
∑ 1/(n+1)  + ∑ 2/(2n +3)
n = 1............n =1