Page 16 - Afrina Indah K. (201933304) dan Afi Choirina M. (201933287) Kel 13 Barisan dan Deret Aritmatika-dikonversi

Kunci Jawaban

A.

1. a = 20 b = U2 – U1 = 15 – 20 = -5
Sn = n (a + Un)
Un = a + (n – 1) b
U20 = 20 + (20-1)(-5)
= 20 + (19) (-5)
= 20 – 95
= – 75
Sn = n (a + Un)
S20 = 20 (20 + (-75))
= 10 (-55)
= – 550 (JAWABAN A)

2. Un = a + (n – 1)b
U6 = a + 5b

= 500 + 5(500)
= 500 + 2500
= 3000

Berarti tabungan Ani pada hari ke-6 adalah Rp 3000 (JAWABAN D)

3. a = 3 b = U2 – U1 = 7 – 3 = 4
Un = a + (n−1)b
= 3 + (n−1)(4)
= 4n – 1
Sn= ½n [(2a + (n −1)b]
= ½n [(2x3 + (n −1)4]
= ½n [(6 + (n −1)4]

= 2n² + n (JAWABAN C)

4. a = 1 b = U2 – U1 = 2 – 1 = 1
Un = a + (n – 1)b
U15 = 1 + (15 – 1)(1)
= 15 (JAWABAN A)

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