Jawabanmu

2014-02-17T23:59:45+07:00
A= 17
b= 20-17
  = 3
Sn = ½ n (2a + (n-1)b)
S30 = ½ 30 (2.17 + 29. 3)
S30 = 15(121) S30
       = 1815
1 3 1