Question

Minta bantuannya :)
Diketahui deret geometri U2 = 6 dan U4 = 54
Tentukan a, r, dan s9 !
Terima kasih atas jawabannya

Answer 1

Mencari nilai r

U4 = ar^3
U2 = ar

54 = ar^3
 6 = ar

9 = r^2
r = akar 9
r = 3

mencari nilai a
U2 = a.r
6 = a.3
a = 6/3
a = 2

mencari s9
S9 = a ( r^n-1) / r - 1
S9 = 2 (3^9 - 1) / 3-1
S9 = 2 (19682) /2
S9 = 19.682

Answer 2

Deret geometri:

U2 = 6 ⇔ ar = 6
U4 = 54 ⇔ ar³ = 54

ar³ = 54
ar = 6
------------ :
r² = 9
r = √9
r = 3

subtitusi:
ar = 6
a3 = 6
3a = 6
a = 6/3
a  = 2

Sn = [U1(r^n - 1)] / [r - 1]
S9 = [2(3^9 - 1)] / [3 - 1]
S9 = [2(19683 - 1)] / [2]
S9 = [2(19682)] / [2] ⇔ coret 2
S9 = 19682