suatu barisan aritmatika diketahui U6= 18 dan U10 = 30 jumlah 16 suku pertama barisan tersebut adalah....

[tex]u6 = 18 \\ a + 5b = 18 \\ \\ u10 = 30 \\ a + 9b = 30 \\ \\ a + 9b = 30 \\ a + 5b = 18 \\ - - - - - - - \\ 4b = 12 \\ b = 3 \\ \\ a + 5(3) = 18 \\ a = 18 - 15 = 3[/tex]
[tex]s16 = \frac{16}{2} (2(3) + 15(3)) \\ s16 = 8 (6+ 45) \\ s16 = 8(51) = 408[/tex]