3,7,11,15,19,......suku ke 20 dri barisn tsb adlh....

Mapel : Matematika

Kelas : 9

Bab : Barisan dan Deret Bilangan
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3, 7, 11, 15, 19

→ Nilai a = 3

→ Beda barisan = 7 - 3 = 4


Maka, nilai suku ke - 20 barisan

Un = a + (n - 1)b

U20 = 3 + (20 - 1)(4)

U20 = 3 + 19(4)

U20 = 3 + 76

U20 = 79 ✔

u1= 3
b = 7-3
=4
un = a+(n-1).b
= 3+(20-1).4
= 79