Ass tolong di bantu

u3 = a + (3 - 1)b
3 = a + 2b .....(1)

u8 = a + (8 - 1) b
13 = a + 7b .....(2)


pers (1) dan (2)
a + 7b = 13
a + 2b = 3
__________-
5b = 10
b = 10/5
b = 2

a + 2b = 3
a + 2(2) = 3
a + 4 = 3
a = 3 -4
a = -1

u10 = -1 + (10 -1) 2
u10 = -1 + 18
u10 = 17

u60 = -1 + (60 - 1) 2
u60 = -1 + (59)2
u60 = -1 +118
u60 = 117