suatu barisan aritmatika diketahui U6=18 U10=30.jumblah 16 suku pertama dari barisan tersebut adalah

Mapel : Matematika

Kelas : 9

Bab : Barisan dan Deret Bilangan
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⏩Beda Barisan

U10 - U6 = 30 - 18
10b - 6b = 12
4b = 12
b = 12/4
b = 3

⏩Suku Pertama
U6 = 18
a + 5b = 18
a + 5(3) = 18
a = 18 - 15
a = 3

Maka, Jumlah 16 suku pertama

Sn = n/2 [2a + (n - 1)b]

S16 = 16/2 [2(3) + (16-1)(3)]

S16 = 8 [6 + 45]

S16 = 8 x 51

S16 = 408

U6 = a + 5b = 18
U10 = a + 9b = 30
------------------ -
-4b = -12
b = 3

a + 5b = 18
a + 5(3) = 18
a + 15 = 18
a = 3

U16 = a + 15b
= 3 + 15(3)
= 3 + 45
= 48

S16 = 16/2 ( a + U16)
=16/2 ( 3 + 48 )
= 8( 51 )
= 408