U2=3 dan u4=⅓ maka nilai u6adalah

U2 = a + b
a + b = 3 •••• (1)

U4 = a + 3b
a + 3b = 1/3
3 ( a + 3b ) = 1
3a + 9b = 1 •••• (2)

a + b = 3 | ×3 |
3a + 9b = 1 | ×1 |
----------------------
3a + 3b = 9
3a + 9b = 1
---------------- -
••••• -6b = 8
••••• b = 8/-6
••••• b = -4/3

a + b = 3
a + (-4/3) = 3
-4/3a = 3
-4a = 9
a = -9/4

Maka,
U6 = a + 5b
•••• = -9/4 + 5 (-4/3)
•••• = -9/4 - 20/3
•••• = -27/12 - 80/12
•••• = -107/12