suku ke -5=-6 suku ke -9=-9 dit=tentukan suku ke 10

U5 -----> a + 4b = - 6
U9 -----> a + 8b = - 9
             ------------------ -
                  - 4b = 3
                      b = - 3/4
a + 4b = -6
a + 4(-3/4) = - 6
a = - 6 + 3
   = - 3

U10 = a + 9b
        = - 3 + 9(-3/4)
        = - 12/4 - 27/4
        = - 39 / 4
        = - 9,75

Rumus :
Un =
[tex]a \: + (n \: - 1)b[/tex]

U5 = a + 4b = -6
U9 = a + 8b = -9
------------------------ (-)
-4b = 3
b = -3/4

a + 4b = -6
a + 4 × (-3/4) = -6
a -3 = -6
a = -3

U10 = a + 9b
= -3 + 9 × (-3/4)
= -3 - 27/4
= -3 -6 3/4
= -9 3/4
= -39/4