Dalan sebuah barisan geometri diketahui S2 = 6 Dan S4 = 30. Hitunglah nilai dari U10 ?

S2 = 6 => a(r^2 - 1)/(r-1) = 6

S4 = 30 => a(r^4 - 1)/(r-1) = 30

S4/S2 = 30/6
(a(r^4 - 1)/(r-1)) / (a(r^2 - 1)/(r-1)) = 5
r^4 - 1 / r^2 - 1 = 5
(r^2 - 1)(r^2 + 1) / (r^2 - 1) = 5
r^2 + 1 = 5
r^2 = 4
r^2 = 2^2
r = 2
(ambil r positif karna jumlahnya positif)

S2 = 6
a(2^2 - 1)/(2-1) = 6
a(4-1)/1 = 6
a×3 = 6
a = 6/3
a = 2

U10 = a×r^9 = 2×(2^9) = 2^10 = 1.024