Diketahui barisan aritmetika 9,14,19,24,.....,154. Banyak suku barisan tersebut ????

[tex] U_1 = a = 9 \\ U_2 = a + b = 14 \\ U_3 = a + 2b = 19 \\ {...} \\ a = 9 \\ b = U_2 - U_1 = 14 - 9 = 5 \\ {} \\ U_n = a + (n - 1)b = 154 \\ U_n = 9 + (n - 1)5 = 154 \\ (n - 1)5 = 154 - 9 \\ (n - 1)5 = 145 \\ n - 1 = 145/5 \\ n - 1 = 29 \\ n = 30 [/tex]