Tentukan rumus suku ke N dari barizant: A. 4, 13, 22, 31, ... B. 5, 8, 11, 14, ... C. 0, 3, 8, 15, ... D. 2, 6, 12, 20, ... E. 200, 190, 180, 170, ...

a.4, 13, 22, 31, ...
U1 = 4 = 9 × 1 - 5
U2 = 13 = 9 × 2 - 5
U3 = 22 = 9 × 3 - 5
Un = 4n - 5
b 5, 8, 11, 14, ...
U1 = 5 = 3 × 1 + 2
U2 = 8 = 3 × 2 + 2
U3 = 11 = 3 × 3 + 2
Un = 3n + 2
c 0, 3, 8, 15, ...
Un = an² + bn + c
U1 = 0 <> a × 1² + b × 1 + c = a + b + c = 0
U2 = 3 <> a × 2² + b × 2 + c = 4a + 2b + c = 3
U3 = 8 <> a × 3² + b × 3 + c = 9a + 3b + c = 8
4a + 2b + c = 3
a + b + c = 0
---------------------- -
3a + b = 3
9a + 3b + c = 8
a + b + c = 0
---------------------- -
8a + 2b = 8
Yg lain gak tau