Jumlah 10 suku pertama barisan aritmatika 2,5,8,11,.....adalah

[tex]s10 = \frac{n}{2} (2a + (n - 1)b) \\ = \frac{10}{2} (2.2 + (10 - 1)3) \\ = 5(4 + (9.3) \\ = 5(4 + 27) \\ = 5 \times 31 \\ = 155[/tex]

[tex]sn = \frac{n}{2} (2a + (n - 1)b)) \\ \\ s10 = \frac{10}{2} (2 \times 2 + (10 - 1) \times 3)) \\ \: \: \: \: \: \: \: \: = 5(4 + 27) \\ \: \: \: \: \: \: \: \: = 5(31) \\ \: \: \: \: \: \: \: \: = 155[/tex]