Jumlah n suku pertama deret aritmetika adalah Sn=n²-3n. Tentukan suku ke 10!

Jumlah n suku pertama deret aritmetika adalah Sn=n²-3n. Tentukan suku ke 10!

Jawaban yang benar adalah 16

Konsep:
Un = Sn – S(n – 1)

ket:
Un = suku ke n
Sn = jumlah suku ke n
S(n-1) = jumlah suku ke (n – 1)

Pembahasan,

Diketahui:
Sn= n² – 19n

Ditanya,
U10 = …

Jadi,

S10 = 10² – 3(10)
S10 = 100 – 30
S10 = 70

S9 = 9² – 3(9)
S9 = 81 – 27
S9 = 54

Jadi,
U10 = S10 – S9
U10 = 70 – 54
U10 = 16

Jadi, suku ke 10 adalah 16

Rekomendasi lainnya :

Baca Juga :  Miss Silvia works at Graha Hospital. She looks after sick children at night. She starts to work at 10 p.m. and finishes at 7 o'clock in the morning. She goes to work by a motorcycle. She has twenty children in her section. She stays up all night. She looks at the children many times during the night. She sometimes sits and talks to a child. The children sleep most of the time. She usually wakes up them at 5 a.m. and gives them breakfast at 6 a.m. After that, she goes home at 7 a.m. Although she feels very tired, she loves her job
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