Jawabanmu

2014-02-24T17:12:28+07:00
Un = 5n-3 
U1 = 5 - 3 = 2 ---> a
U2 = 10-3 = 7
Beda = U2-U1 = 7-2 = 5

Sn = n/2 ( 2a + (n-1)b )
S12 = 12/2 (2.2 + 11.5)
       = 6 ( 4 + 55 )
       = 354
2 1 2
2014-02-24T17:17:44+07:00
U1 : 2
U2 : 7
U3 : 12
U4 :17
U5 :23
U6 : 27
U7 :32
U8 :37
U9 :42
U10 :47
U11 :52
U12 : 57
3 4 3