tiga suku dari barisan 1,9,36,100 adalah

1,9,36,100
= 1² , 3², 6² , 10²
B1 = 2 , 3 , 4
B2 = 1 , 1

2a = 1
a = ½
b = ½
c = 0
Un = ½n(n+1)
U4 = 4/2(4+1) = 10
U4² = 10² = 100
U5 = 5/2(5+1) = 15
U6 = 6/2(6+1) = 21
U7 = 7/2(7+1) = 28

3 suku = 15² , 21² , 28²
= 225, 441 , 784