bantuin donk
1. diketahui U9 = 27 dan U13 = 43 tentukan U20 dan S7
1. diketahui U9 = 27 dan U13 = 43 tentukan U20 dan S7
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Penjelasan dengan langkah-langkah:
u9 = 27
u13 = 43
un = a + (n - 1)b
u9 = a + (9 - 1)b
27 = a + 8b
un = a + (n - 1)b
u13 = a + (13 - 1)b
43 = a + 12b
a. Cari b
a + 8b = 27
a + 12b = 43
___________ _
-4b = -16
b = 4
b. Cari a
a + 8b = 27
a + 8(4) = 27
a = 27 - 32
a = -5
c. Nilai u20
un = a + (n - 1)b
u20 = (-5) + (20 - 1) . 4
u20 = (-5) + (19 x 4)
u20 = -5 + 76
u20 = 71
d. Nilai s7
Sn = n/2 . (2a + (n - 1)b)
S7 = 7/2 . (2(-5) + (7 - 1) . 4)
S7 = 7/2 . (-10 + (6 x 4))
S7 = 7/2 . (-10 + 24)
S7 = 7/2 . 14
S7 = 49
Verified answer
Jawaban:
U20 = 71
S7 = 49
Penyelesaian:
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