Plissss jawab nomer 1-4 ya soalnya buat besokkkkk pagi...

1) tegal. : a = 2000
b = 200
un = 2000+(n-1)200
= 2000+200n-200
= 200n+1800

brebes : a = 4000
b = 100
Um = 4000+(n-1)100
= 4000+100-100
= 100n+3900

a) un = um
200n+1800 = 100n+3900
100n. = 2100
n = 21

1 thn = 12 bln
Bulan ke 21 = 21-12
= 9 (Sept)

b) bulan jun = bulan ke 6
U6 = 200(6)+1800
= 1200+1800
= 3000

c) tegal:
U12 = 200(12)+1800
= 2400+1800
= 4200
S12 = ½.n(a+u12)
= ½.12 (2000+4200)
= 6 (6200)
= 37.200

Brebes :
U12 = 100n+3900
= 100(12)+3900
= 1200+3900
= 5100

S12 = ½n (a+u12)
= ½.12 (4000+5100)
= 6 (9100)
= 54600