tolong jawab(7&8) yaa beserta carany... makasih..

No.7
U2 = 8, U5 = 64

Rumusnyaa: un = a.r^n-1 (^ = pangkat)

U2 = a.r^1 = a.r = 8
U5 = a.r^4 = a.r^4 =64

U5:U2 --> r^3 = 8 --> r= 2

Subs r=2 ke u2
a.r = 8
a = 8:r = 8:2=4

Suku k-13 = a.r^12 = 4.2^12 = 16384

No.8

Rumus: un= a.r^n-1

(terbagi jd 6bag)
Terpendek = 3cm --> a.r^0 = 3 --> a=3
Terpanjang = 96cm --> a.r^5 = 96

Subs a=3 ke a.r^5 =96
3.r^5 = 96
r^5 = 96:3 = 32
Maka r=2

S6 = a(1-r^6): (1-r)
S6 = 3(1-2^6): (1-2)
S6 = 3(1-64): (-1)
S6 = 189

Jadi, panjang tali semula adlh 189cm

Sori kalo salah hehe thx