Question

Diketahui barisan : 92, 85,78,71,....,maka S50 (jumlah 50 suku pertama) adalah​

Answer 1

Penjelasan dengan langkah-langkah:

beda

= u2-u1

= 85-92

= -7

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

S50 = 50/2(2(92) + (50-1)(-7))

S50 = 25(184 + 49(-7))

S50 = 25(184 + (-343))

S50 = 25(-159)

S50 = -3.975

Answer 2

Penjelasan dengan langkah-langkah:

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

S50 = 50/2.(2(92) + (50 - 1)(85 - 92)

S50 = 50/2.(184 + 49(-7)

S50 = 50/2.(184 + (-343)

S50 = 50/2.(-159)

S50 = 25.(-159)

S50 = -3975