Rumus suku ke-n dari barisan 1,10,25,46

1,10,25,46,
B1 = (10-1), (25-10) , (46-25)
B1 = 9,15,21
B2 = (15-9) , (21-15)
B2 = 6, 6

2a = 6
a = 3

3a + b = 9
3x3 + b = 9
b = 0

a + b + c = 1
3 + 0 + c = 1
c = 1-3 = -2

Un = an² +bn + c
Un = 3n² + 0xn -2
Un = 3n² - 2