un= 1/2 n (2n+2) mencari U1 sampai U5

- Barisan dan Deret -

Un = ½n (2n+2)

U1 = ½(1) (2(1)+2) = ½(4) = 2
U2 = ½(2) (2(2) +2) = 1(6) = 6
U3 = ½(3) (2(3) +2) = 3/2(8) = 12
U4 = ½(4) (2(4) +2) = 2(10) = 20
U5 = ½(5) (2(5) +2) = 5/2(12) = 30

semoga membantu
-vin