Ass kak minta bantuannya pake cara ya:-)

DERET ARITMATIKA

3, 5, 7, 9, 11,....

Ditanya jumlah 40 suku pertama

Jawaban :
========

Nilai a = 3
Nilai b = 5 - 3 = 2

Maka :

S40 = n/2 (2a + (n-1)b)

S40 = 40/2 ( 2 x 3 + (40-1)(2))

S40 = 20 (6 + 78)

S40 = 20 x 84

S40 = 1680 (Jawaban A)

a = 3
b = 2

Sn = n/2 ( 2a + ( n - 1 ) b )
S₄₀ = 40/2 ( 2(3) + ( 40 - 1 ) 2 )
S₄₀ = 20 ( 6 + 39(2) )
S₄₀ = 20 ( 6 + 78 )
S₄₀ = 20 ( 84 )
S₄₀ = 1680 [ Opsi. A ]

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