please help me,jawab nomor 8,10,12 beserta caranya

8.
1/(3 - akar 8) × (3 + akar 8) / (3 + akar 8)
= (3 + akar 8) / (3^2 - 8)
= 3 + akar 8
= 3 + 2 akar 2

10.
Deret geometri
a = 2
r = 2

Un = ar^(n-1)
Un = 2.2^(n-1)
Un = 2^n

12.
T = 3D

5T + 10D = 125000
5 . 3D + 10D = 125000
15D + 10D = 125000
25D = 125000
D = 5000

T = 3 × 5000 = 15000

15T + 20D
= 15 x 15000 + 20 × 5000
= 225000 + 100000
= 325.000