Question

tolong dijawab
yang benar
pake cara
secepatnya

Answer 1

Un = a + (n - 1)b
U3 = a + (3-1)b
8 = a + 2b
___________

Un = a + (n-1)b
U12 = a + (12 -1)b
62 = a + 11b

Tahap eliminasi

62 = a + 11b
8 = a + 2b
_________ __
54 = 9b
b = 54/9
b = 6 -----> ketemu bedanya


8 = a + 2b
8 = a + 2 x 6
8 = a + 12
a = 8 -12
a = -4
Cari U20

U20 = a + ( 20 -1)b
U20 = - 4 + 19 x 6
U20 = - 4 + 114
U20 = 110

Cari S20
S20 = 20/2 ( 2 x -4 + ( 20 -1)6)
S20 = 10(-8 + 19 x6)
S20 = 10 (-8 + 114)
S20 = 10 x 106
S20 = 1060