tolong bantu yaa kaaaaa

19;
a = 4000
b = 2000
S24 = 24/2(2x4000 + (24-1)2000)
S24 = 12 (8000 + 46.000)
S24= 12x 54.000
S24= 648.000 (C)

20.
suku berikutnya
5 + 3 = 8
8 + 5 = 13
13 + 8 = 21
jawaban C

21.
U9 = 3(9²) + 9 = (3x81)+9 = 243 + 9 = 252
U5 = 3(5²)+ 5 = (3x25) + 5 = 75+5 = 80
U9 - U5 = 252 - 80 = 172 (A)

22.
a = 99
b = 93-99= -6
U22 = 99 + (22-1)(-6)
= 99 + (21x(-6))
= 99 - 126
= -27 (A)

23.
pola bilangan persegi panjang
Un = n(n+1)
U20 = 20(20+1)
= 20x21
= 420 (B)

24.
U7-U3 = 37-9
6b-2b = 28
4b = 28
b = 7

U3= 9
a + 2b = 9
a + 2x7 = 9
a + 14 = 9
a = -5
U30 = -5 + 29 x7 = -5 + 203 = 198 (A)

25.
2 jam = 120 menit
n = 120/20 = 6
15 + 30 + 60 + 120 + 240+ 480= 945
jawaban tidak ada di pilihan