diketahui barisan bilangan U5 =12 dan U9 = 30 . tentukan suku ke - 12

U9 = a +8b = 30

U5 = a+4b = 12
.............................-
4b = 18
b = 4,5
a = -6

U12 = a+11b = -6 + 11.45 = -6+49,5 = 43,5