Question

Kuis +50:
{p, p-4, p-8} membentuk deret aritmatika
Jika jumlah 6 suku pertamanya adalah 132, tentukan:

Jumlah 4 suku pertama deret aritmatika tersebut!
Jawab = .......

Answer 1

Jawaban:

Diketahui :

a = p

b = -4

S6 = n/2 (2a + (n - 1)b) = 132

S6 = 6/2 (2p + (6 - 1)-4) = 132

S6 = 3 (2p + (5)-4) = 132

S6 = 3 (2p - 20) = 132

S6 = 6p - 60 = 132

6p - 60 = 132

6p = 132 + 60

6p = 192

p = 32

S4 = 4/2 (2(32) + (4 - 1)-4)

= 2 (64 + (3)-4)

= 2 (64 - 12)

= 2 (52)

= 104

Semoga membantu

Answer 2

Menentukan beda:

• b = p - 4 - p = -4

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

132 = 6/2(2p + (6 - 1)-4)

132 = 3(2p - 20)

132 = 6p - 60

6p = 132 + 60

6p = 192

p = 192/6

p = 32

..

Suku pertama = p = 32

Maka,

S4 = 4/2(2(32) + (4 - 1)-4)

S4 = 2(64 - 12)

S4 = 2(52)

S4 = 104