tolonglah ya... barisan geometri tuh! pakai caranya Ok!

U2 = ar
U4 = ar³

144 = U2 × U4
144 = ar × ar³
144 = a²r⁴
√144 = √(a²r⁴)
12 = ar²
U3 = ar² = 12 → a = 12/r²

a = 12/r²

misal r = 2
a = 12/2²
a = 12/4
a = 3

U8 = ar^7
= 3 × 2^7
= 3 × 128
= 384