2,7,16,29.........tentukan suku ke 9

Bab Barisan dan Deret
Matematika SMP Kelas VIII

2, 7, 16, 29, ... → a = 2
  5,  9,  13, ...→ b = 5
     4,  4, .. → c = 4

Un = a + (n - 1) x b + 1/2 x (n - 1) x (n - 2) x c

U9 = 2 + (9 - 1) x 5 + 1/2 x (9 - 1) x (9 - 2) x 4
      = 2 + 8 x 5 + 1/2 x 8 x 7 x 4
      = 2 + 40 + 112
      = 154