tolong menggunakan langkah
Penjelasan dengan langkah-langkah:
14. Menurut saya, soal di atas salah
1, 5, 9, 13, ..., 61
a= 1
a= 1 b = 5 - 1 = 4
a= 1 b = 5 - 1 = 4Un = 61
Un = a + (n - 1)b
61 = 1 + (n - 1) 4
61 = 1 + 4n - 4
61 = 4n - 3
64 = 4n
16 = n
Jadi ada 16 suku
Jawabanny B. 16
15. 17, 13, 9, 5, ...
a = 17
b = 13 - 17 = -4
S5 = ???
Un = a + (n - 1)b
U5 = a + 4b
U5 = 17 + 4(-4)
U5 = 1
Sn = n/2 (a + Un)
S5 = 5/2 (a + U5)
S5 = 5/2 (17 + 1)
S5 = 5/2 (18)
S5 = 5(9)
S5 = 45
Jawabannya B. 45
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