No 1&2 mohon dibantu kak
Jawaban Terkonfirmasi
Nomor 1
Ini adalah deret aritmatika.
a= log 5
log 5 + b = log 55
b = log 55 – log 5
b = log (55/5)
b = log 11
S50 = 50/2 (2×log 5 + 49×log11)
= 25(2×log 5 + 49×log11)
= 50×log5 + 1225×log11
= log5⁵⁰ + log11¹²²⁵
= log(5⁵⁰ × 11¹²²⁵)
= log(25²⁵ × 11¹²²⁵) (A)
Nomor 2
S5 = 35
S4 = 24
U5 = S5-S4 = 35 – 24 = 11
a + 4b = 11
a = 11 – 4b
S4 -> 4/2 (2(11 – 4b) + 3b) = 24
2(22 – 8b + 3b) = 24
22 – 5b = 12
-5b = -10
b = 2
a = 11 – 4 × 2
= 11 – 8 = 3
U15 = 3 + 2×14
= 3 + 28 = 31 (A)