Banyak kubus k1 = 6 kubus, k2= 15 kubus , k3 =28 kubus dan seterusnya . a) berapa bnyak susunan kubus k4? b) berapa banyak susunan kubus k10?

susunan kubus =
6, 15 , 28, ....
B1 = 9 , 13
B2 = 4

2a = 4
a = 4/2
a = 2

3a + b = 9
3x2 + b = 9
b = 9-6 = 3

a+b+c = 6
2+3+c = 6
c = 1

Un = 2n² + 3n + 1

k4 = 2(4)² + 3(4) + 1 = 32+13 = 45
k10 = 2(10)² + 3(10) + 1 = 200+31 = 231