Question

Tentukan rumus suku ke (n+1) dari barisan 1,4,10,19,31

Answer 1

1,4,10,19,31
bd1 = 3,6,9,12
bd2 = 3,3,3

2a = 3
a = 3/2

3a + b = 3
9/2 + b = 6/2
b = (6-9)/2 = -3/2

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

Un = 3n²/2 -3n/2 +1
Un = 3n(n-1)/2 + 1