diketahui suku ke-5 = -6 suku ke-6 negatif 9 Tentukan suku ke negatif 10 barisan tersebut

Bab : Baris Dan Deret
Kelas : IX SMP

U5 = U1 + 4b = -6
U6 = U1 + 5b = -9
•••••••••••••••••••••••
========>-b = 3
========> b = -3

U5 = U1 + 4b
-6 = U1 + 4(-3)
-6 = U1 - 12
U1 = -6 - (-12)
U1 = -6 + 12
U1 = 6

Un = U1 + (n-1) b
U-10 = 6 + (-10 - 1) (-3)
U-10 = 6 + (-11) ( -3)
U-10 = 6 + 33
U-10 = 39

*Pahami soal
*Jika Baris minus => positive
*Jika baris positive makin besar => Negative