diketahui suatu barisan aritmatika U3 + U9 + U11 = 75. Tentukan U43 ! jika U22 adalah 68

143... 75 dtmbh 68 cm gt

jawab

u3 + u9 + u11 = 75
a + 2b +a + 8b + a + 10 b = 75
3a + 20 b = 75...(i)

u22 = 68
a + 21 b = 68...(ii)

(i) dan (ii)
3a + 20 b = 75
a  + 21 b = 68 .....}kalikan 3

3a + 20 b = 75
3a + 63b = 204...||(-)
-43 b = -129
b = 3

a +21b = 68
a = 68 - 21b
a = 68 - 21(3)
a = 5

u43 = a + 42 b
u43 = 5 + 42(3)
u43 = 131