Suku ke 12 dari barisan aritmetika: 24,21,18,15,...adalah...

b = -3
a = 24

U12 = 24 + 11 × (-3)
U12 = 24 - 33
U12 = -9

[tex]u12 = a + (n - 1)b \\ u12 = 24 + (11) - 3 \\ u12 = 24 - 33 \\ u12 = - 9[/tex]