ada yang ngerti gk buat bsk di kumpulin

no 6 A
maaf kalo salah

6) A
[tex]4 = {4}^{1} \\ 16 = {4}^{2} \\ 64 = {4}^{3} [/tex]
brarti rumusnya :
[tex] {4}^{n} [/tex]
7) B
U1 = 32 = a
U3 = 8 -> a × r^2 = 8
32 × r^2 = 8
r^2 = 8/32
r = √1/4 = 1/2

Karna r < 1 maka rumusnya : (Geometri)
[tex]sn = \frac{a \times ( 1 - {r}^{n}) }{1 - r} [/tex]
[tex]s5 = \frac{ 32 \times (1 - \frac{1}{2}^{5}) }{1 - \frac{1}{2} } [/tex]
[tex]s5 = \frac{32 \times \frac{31}{32} }{ \frac{1}{2} } = \frac{31}{ \frac{1}{2} } = 62 [/tex]
8) B
U1 = 5 = a
b = U2-U1
= 8 - 5
= 3

Rumus Un: (Aritmatika)
Un = a + (n-1) × b
68 = 5 + (n-1) × 3
68 = 5 + 3n - 3
68 = 2 + 3n
3n = 66
n = 22


9) E
U3 = 5
U7 = 13
Ditanya: S12 = ?

U3 = a + 2b = 5
U7 = a + 6b = 13

Eliminasi:
a + 6b = 13 a + 2b = 5
a + 2b = 5 a + 2×2 = 5
--------------- - a + 4 = 5
4b = 8 a = 1
b = 2

Rumus Sn: (Aritmatika)
[tex]sn = \frac{n}{2} (2a + (n - 1) \times b)[/tex]
[tex]s12 = \frac{12}{2} (2 \times 1 + (12 - 1) \times 2 \\ s12 = 6 \: (2 + 11 \times 2) \\ s12 = 6(2 + 22) \\ s12 = 6 \times 24 = 144[/tex]