105, 109, 113, . . ., 185 banyaknya suku barisan diatas

Mapel : Matematika

Kelas : 8, 9

Bab : Barisan dan Deret Bilangan
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→ nilai a = 105

→ nilai b = 109 - 105 = 4

→ Un = 185


Ditanya → banyak suku (n) =...?

Jawaban '
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Un = 185

a + (n - 1)b = 185

105 + (n - 1)(4) = 185

105 + 4n - 4 = 185

4n = 185 - 101

4n = 84

n = 84/4

n = 21✔