suku ke 6 dan ke 8 barisan aritmatika berturut turut 10dan -38 suku ke 12 barisan tersebut adalah

Mapel : Matematika
Bab : Barisan dan Deret

Barisan Aritmatika

Un = bn + a - b
U6 = 6b + a - b
 10 = 5b + a

Un = bn + a - b
U8 = 8b + a - b
-38 = 7b + a

10 = 5b + a
-38 = 7b + a
----------------- -
48  = -2b
   b = 48/-2
   b = -24

10 = 5b + a
10 = 5(-24) + a
10 = -120 + a
  a = 10 + 120
  a = 130

Un = bn + a - b
U12 = -24(12) + 130 - (-24)
U12 = -288 + 130 + 24
U12 = -288 + 154
U12 = -134

Aritmetika

Un = a + (n - 1)b

U6 = a + (6 - 1)b
= a + 5b
= 10

U8 = a + (8 - 1)b
= a + 7b
= -38

a + 5b = 10
a + 7b = -38
_________ _
-2b = 48
b = -24

a + 5b = 10
a + 5(-24) = 10
a + (-120) = 10
a = 130

U12 = 130 + (12 - 1)(-24)
= 130 + 11(-24)
= 130 + (-264)
= -134