Hasil dari 8+15+22+...+176 adalah

Deret aritmatika
a = 8
b = 7
Un = 176

Cari nilai n???
Un = a + (n-1)(7)
176 = 8 + 7n - 7
176 = 1 + 7n
176-1 = 7n
175 = 7n
175/7 = n
25 = n

Maka :
Sn = n/2 (a + Un)
S25 = 25/2 (8 + 176)
S25 = (25/2) *(184)
S25 = 2300

a = 8
b = 15 - 8 = 7
Un = 176
Dit. Sn ?
penyelesaian:
• Un = a + (n-1)b
176 = 8 + (n-1)7
176 = 8 + 7n - 7
176 = 7n + 1
7n = 175
n = 25
• Sn = n/2 (a + Un)
= 25/2 ( 8 + 176)
= 25/2 (184)
= 25 x 92
= 2300