Question

Hitung jumlah deret aritmatika yang suku pertamanya= 10, suku terakhir=370 dan U12-U9= 72

Answer 1

U1= a = 10

u12-u9 = 72
a + (12-1)b -[a+(9-1)b] = 72
11b-8b =72
3b = 72
b = 24

un = 10 + (n-1)24
370 = 10 + (n-1)24
360 = 24n - 24
384 = 24n
n= 16

sn = 16/2 (a + U16)
= 8(10+370)
=3040