Sn = 2n2 – 5n Tentukan 5 suku pertama Terima kasih

Sn = n/2 (a + Un)

S1 = a = U1

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Sn = 2n² – 5n
Sn = n(2n – 5)
S1 = 2 – 5
S1 = -3

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Sn = n(2n – 5)
n/2 (S1 + Un) = n(2n – 5)
S1 + Un = 2(2n – 5)
Un = 4n – 10 – S1
Un = 4n – 10 – (-3)
Un = 4n – 7

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U1 = 4(1) – 7 = -3
U2 = 4(2) – 7 = 1
U3 = 4(3) – 7 = 5
U4 = 4(4) – 7 = 9
U5 = 4(5) – 7 = 13