suku ke dua = 5 jika suku u4 + u6 = 28 , suku ke 9 ?

U2 = 5
U4+U6 = 28 shg U5 = 28/2 =14
b = (14-5)/(5-2) = 9/3 = 3

U9 = U5+4b = 14 + 4(3) = 14 + 12 = 26

a + b = 5
(a + 3b) + (a + 5b) = 28
2a + 8b = 28
a + 4b = 14

eliminasi:
a + 4b = 14
a + b = 5
_________ -
3b = 9
b = 3
a = 2
U9 = a + 8b
= 2 + 24
= 26