Tolongin yah no 11-13 harus di kumpulin besok

11.
1 , 10 , 25 , 46
..+9…+15…+21
…….+6…..+6

a = 1
b = 9
c = 6

Un = a + (n – 1)b + 1/2(n² – 3n + 2)c
Un = 1 + (n – 1)9 + 1/2(n² – 3n + 2)6
Un = 1 + 9n – 9 + 3n² – 9n + 6
Un = 3n² – 2

12.
3, 6, 12, 24. …
a = 3
r = 6 : 3 = 2

Un = a. rⁿ⁻¹
Un = 3 . 2ⁿ⁻¹
Un = 3/2 . 2ⁿ

13.
U9 – U5 = 20 – 8
a + 8b – (a + 4b) = 12
4b = 12
b = 12 : 4
b = 3

a + 4b = 8
a + 4(3) =8
a + 12 = 8
a = 8 – 12
a = -4

U10 = a + 9b
U10 = -4 + 9(3)
U10 = -4 + 27
U10 = 23