gimana cara mencari panjang mula2?

U1 = a= 9
U6 = ar^5 = 288

U6/U1 = ar^5/r = 288/9
r=2

S6= a(r^n-1)/(r-1)
S6 = 9(63)/1
S6 = 567cm

Cari rasionya dulu
u6-u1 = 288:9
R pangkat 5= 32
R pangkat 5= 2 pangkat 5
R = 2

U1 = 9
U2 = 9x2 =18
U3 = 18x2 = 36
U4 = 36x 2 = 72
U5 = 72x2 = 144
U6 = 144x2 = 288

Pamjang tali mula mula
9+18+36+72+144+288 = 567 cm