tentukan 5 suku pertama dari barisan bilangan berikut. (u-1)(2n+1)

U1 = (1-1)(2x1+1) = 0 x (2+1) = 0 x 3 = 0
U2 = (2-1)(2x2+1) = 1 x (4+1) = 1 x 5 = 5
U3 = (3-1)(2x3+1) = 2 x (6+1) = 2 x 7 = 14
U4 = (4-1)(2x4+1) = 3 x (8+1) = 3 x 9 = 27
U5 = (5-1)(2x5+1) = 4 x (10+1) = 4 x 11 = 44

Un = ( u - 1 ) ( 2n + 1 )

U1 = ( (1) - 1 ) ( 2(1) + 1 )
U1 = ( 1 - 1 ) ( 2 + 1 )
U1 = ( 0 ) ( 3 )
U1 = 0

U2 = ( (2) - 1 ) ( 2(2) + 1 )
U2 = ( 2 - 1 ) ( 4 + 1 )
U2 = ( 1 ) ( 5 )
U2 = 5

U3 = ( (3) - 1 ) ( 2(3) + 1 )
U3 = ( 3 - 1 ) ( 6 + 1 )
U3 = ( 2 ) ( 7 )
U3 = 14

U4 = ( (4) - 1 ) ( 2(4) + 1 )
U4 = ( 4 - 1 ) ( 8 + 1 )
U4 = ( 3 ) ( 9 )
U4 = 27

U5 = ( (5) - 1 ) ( 2(5) + 1 )
U5 = ( 5 - 1 ) ( 10 + 1 )
U5 = ( 4 ) ( 11 )
U5 = 44

Jadi, 5 suku pertama dari barisan bilangan ( u - 1 ) ( 2n + 1 ) adalah = { 0 , 5 , 14 , 27 , 44 }