rumus umum barisan 4,10,20,34, 0....adalah

4 10 20 34
6 10 14
4 4

a + b + c = 4
3a + b = 6
2a = 4
a = 4/2 = 2
3a + b = 6
3×2 + b = 6
6 + b = 6
b = 6 - 6 = 0
a + b + c = 4
2 + 0 + c = 4
c = 4 - 2 = 2
Un = an^2 + bn + c
= 2n^2 + 0 + 2
= 2n^2 + 2
jadi rumus umum barisan itu adalah
2n^2 + 2