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Jawaban Terkonfirmasi
9.
U3 = a + 2b = 18
U7 = a + 6b = 38
———————— –
-4b = -20
b = 5
a + 2b = 18
a + 2×5= 18
a + 10 = 18
a = 8
Sn = n/2[2a+(n-1)b]
S24 = 24/2[2×8 + (24-1)x5]
S24 = 12 ( 16 + 23 x 5)
S24 = 12 (16+ 115)
S24 = 12 x 131
S24 = 1.572 (C)
10.
a = 2
b = 8 – 2 = 6
U20 = 2 + (20-1)x6
U20 = 2 + (19 x 6)
U20 = 2 + 114
U20 = 116 (C)
11.
suku pertama = -3
beda = -5 – (-3)= -5 + 3 = -2
jawaban A
12.
16, 13, 10, 7, 4, …
beda barisan = 13- 16 = -3
maka suku berikutnya
4 – 3 = 1
1 – 3 = -2
jawaban D