minta tolong lagi ya...ane rela ngabisin poin biar bisa tau gimana ngerjainnya.tolong.no 9 dan 10

9. n = 5
a = 4
Un = 324
Un = arⁿ-¹
4.r⁴=324
r⁴= 81
r = 3
S5 = a(rⁿ - 1)/r - 1
= 4(3^5 - 1 )/ 3-1
= 4 ( 243 - 1)/2
= 4 ( 242 )/2
= 484 cm

10. U1 = 5
U5 = 80
U9 ?

Un = arⁿ-¹
U5 = 5.r⁴ = 80
r⁴ = 14
r = 2
U9 = arⁿ-¹
= 5.2^8
= 5.256
= 1280

9.

4, ..., ..., ..., 324
U1 = 4
U5 = 324

U5 = U1 . r^4
324 = 4 . r^4
324/4 = r^4
81 = r^4
[tex] \sqrt[4]{81} [/tex] = r
3 = r

Sn = U1.( r^n - 1)/r-1    [jika r > 1}
S5 = 4 (3^5 - 1) / 3 - 1
S5 = 4.(243 -1) / 2
S5 = 4.(242) / 2
S5 = 968/2
S5 = 484 (b)

10.
5, ..., ..., ..., 80
U1 = 5
U5 = 80

U5 = U1 . r^4
80 = 5 . r^4
80/5 = r^4
16 = r^4
[tex] \sqrt[4]{16} [/tex] = r
2 = r

Un = U1 . r^n-1
U9 = 5 . 2^9-1
U9 = 5 . 2^8
U9 = 5. 256
U9 = 1280 (d)

semoga bener