Jawabanmu

2014-03-28T06:49:49+07:00
5-3 = 2
7-5 = 2
sterusnyaa......
maaf klo salah, yg ku tau gitu, coz ku masih smp
2014-03-28T07:23:25+07:00
Deret aritmatika 3 + 5 + 7 + ...
a = 3
b = ( U_{1} -  U_{2} )
   = ( 5 - 3)
   = 2

 S_{n} =  \frac{n}{2} (2a + (n-1) b)

 S_{20} =  \frac{20}{2} (2.3 + (20-1) 2)

 S_{20} = 10 (6 + (19) 2)
 S_{20} = 10 (6 + 38)
 S_{20} = 10 (44)
 S_{20} = 440

semoga membantu :)