Jawabanmu

2014-05-11T05:47:43+07:00
Ini deret aritmetika ya?

U2 = 5
a + b = 5 ... persamaan(1)

U4 + U6 = 28
a + 3b + a + 5b = 28
2a + 8b = 28 ..... persamaan (2)
 
2a + 8b = 28
2a + 2b = 10 - ---> hasil x2 persamaan 1
        6b = 18
          b = 18/6 = 3

a+b = 5
a + 3 = 5
a = 5-3 = 2

Jadi,
U9 = a + 8b
     = 2 + 8(3)
     = 2 + 16
U9 = 18

2014-05-11T07:40:06+07:00
U9=a+(n-1)b =2+(9-1)3 =2+8.3 =2+24 =26