Dik; deret aritnetika7+10+13+16+19+22+…tentukanlahA. Suku ke-50Jumlah 100suku

Diketahui :
a = 7
b = 3

Un = a + (n – 1) b
Sn = 1/2n ( a + Un)
* suku ke 50
U50 = 7 + (50 – 1) 3
= 7 + 49 x 3
= 7 + 147
= 154

* jumlah 100 suku
U100 = 7 + (100 – 1) 3
= 7 + 99 x 3
= 7 + 297
= 304

S100 = 50 (7 + 304)
= 50 x 311
= 15.550