suatu barisan aritmatika diketahui U6=18 dan U10=34. jumlah 16 suku pertama barisan tersebut adalah........... a.896 b.512 c.448 d.408

U6 = 18

U10 = 34
U6 + 4b = 34
18 +4b = 34
b = 16/4 = 4

U6 = 18
a + 5b = 18
a + 5(4) = 18
a = 18 - 20 = -2

S16 = n/2 [2a + (n-1)b] = 16/2 [2(-2) +15(4)] = 8 [-4+60] = 8[56] = 448 (C)