Diketahui barisan aritmatika 3,5,7 berapakah jumlah 10 suku pertama dari barisan aritmatika tersebut

MAPEL : MATEMATIKA

KELAS : IX

BAB : BARISAN & DERET
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Diketahui
↪U1 = 3
↪U2 = 5
↪b = 5 - 3 = 2

Ditanya :
↪S10 =....?


Jawaban :
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S10 = n/2 (2*U1 + (n-1)b)

S10 = 10/2 (2 x 3 + (10-1)(2))

S10 = 5 (6 + 18)

S10 = 5 x 24

S10 = 120 ✔

a = 3

b = U₂ - U₁
b = 5 - 3
b = 2

Sn = n/2 ( 2a + ( n - 1 ) b )
S₁₀ = 10/2 ( 2(3) + ( 10 - 1 ) 2 )
S₁₀ = 5 ( 6 + 9(2) )
S₁₀ = 5 ( 6 + 18 )
S₁₀ = 5 ( 24 )
S₁₀ = 120

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