Tuliskan empat suku pertama dan barisan bilangan,jika suku ke-n ditemtukan A)un=5(2n-1) B)un=3n(n+2) C)un=1/2 n(2n+2) D)un=n²(2n+1)

Un = 5 (2n-1)
n = 1 = U1 = 5 x (2(1)-1) = 5 x 1 = 5
n = 2 = U2 = 5 x (2(2) -1) = 5 x 3 = 15
n = 3 = U3 = 5 x (2(3) - 1) = 5 x 5 = 25
n = 4 = U4 = 5 x (2(4) - 1) = 5 x 7 = 35

Un = 3n (n+1)
n = 1 = U1 = 3(1) x (1+1) = 3 x 1 = 3
n = 2 = U2 = 3(2) x (2+1) = 6 x 3 = 18
n = 3 = U3 = 3(3) x (3+1) = 9 x 4 = 36
n = 4 = U4 = 3(4) x (4+1) = 12 x 5 = 60

Un = 1/2 x n (2n + 2)
n = 1 = U1 = 1/2 x 1 (2(1) + 2) = 1/2 (4) = 2
n = 2 = U2 = 1/2 x 2 (2(2) + 2) = 1 x 4 = 4
n = 3 = U3 = 1/2 x 3 (2(3) + 2) = 3/2 x 8 = 24/2 = 12
n = 4 = U4 = 1/2 x 4 (2(4) + 2) = 2 x 10 = 20

Un = n² (2n+1)
n = 1 = U1 = 1² x (2(1) + 1) = 1 x 3 = 3
n = 2 = U2 = 2² x (2(2) + 1) = 4 x 5 = 20
n = 3 = U3 = 3² x (2(3) + 1 = 9 x 7 = 63
n = 4 = U4 = 4² x (2(4) + 1) = 16 x 9 = 144