Deret aritmatika A. U1=4, b=-2, U12=.... B. U1=-15, U5=25, b=....

[A]

dik:
a = 4
b = -2

dit: u12

jawab:
u12 = 4 + (12 - 1)-2
u12 = 4 + (11)-2
u12 = 4 - 22
u12 = -18 ✔️

[B]

dik:
a = -15
u5 = 25

dit: b

jawab:
u5 = a + (5 - 1)b
25 = -15 + 4b
b = 25 + 15 / 4
b = 40 / 4
b = 10 ✔️