tolong dijawab pakai cara jalannya.

menentukan rasio:
Un = a x r^n-1
diketahui:
U2 = 6, U4 = 54

=> Un = a x r^n-1
U2 = a x r^2-1
6 = a x r

=> Un = a x r^n-1
U4 = a x r^4-1
54 = a x r^3
maka
a x r^3 = 54
a x r x r^2 = 54
6 x r^2 = 54
r^2 = 54/6
r^2 = 9
r = √9
r = 3

U2 = 6, U4 = 54
jadi
2, 6, 18, 54, 162, 486
2+6+18+54+162+486 = 728 (d)
semoga membantuu