U4=54
U7=2
a. suku kesembilan
b. jumlah 5 suku pertama
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U7=2
a. suku kesembilan
b. jumlah 5 suku pertama
Penjelasan dengan langkah-langkah:
r^(7-4)=2/54
r³=1/27
r=³√1/27
r=1/3
U9=U7×r²
=2×1/3²
=2×1/9
=2/9
jadikan yang terbaiknya
U4 = 54
U7 = 2
U7 = ar⁶ = 2
U4 = ar³ = 54
ar⁶/ar³ = 2/54
r³ = 1/27
r = ³V(1/27)
r = 1/3
ar³ = 54
a(1/3)³ = 54
a(1/27) = 54
a = 54/(1/27)
a = 54 × 27/1
a = 1458
a] n = 9
Un = ar^(n-1)
U9 = 1458(1/3)^(9-1)
U9 = 1458(1/3)⁸
U9 = 1458(1/6561)
U9 = 2/9
b] n = 5
Sn = a(1 - r^n)/(1 - r)
S5 = 1458(1 - (1/3)⁵)/(1 - 1/3)
S5 = 1458(243/243 - 1/243)/(3/3 - 1/3)
S5 = 1458(242/243)/(2/3)
S5 = 1452/(2/3)
S5 = 1452 × 3/2
S5 = 2178
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