Jawabanmu

Jawaban paling cerdas!
2014-03-19T13:05:30+07:00
A=2/3
U3 ⇒  2/27 = a r²
          2/27 =  2/3 r²
           1/9  = r²
             r  = 1/3

S4 =  \frac{a(1-r^{3}) }{1-r} }
     =  \frac{2/3 (1-  1/3^{4}) }{1-1/3} =  \frac{80}{81}
1 5 1
2014-03-19T13:06:04+07:00
U1 = a = 2/3
U2 = 2/9
U3 = 2/27
U4 = 2/81
Rasionya 3
Sn = a (r pangkat n -1) / r-1
S4 = 2/3 (3 pangkat 4 -1) / 3-1
     = 2/3 (81-1) / 2
     = 2/3 . 79 / 2
     = 2/3 . 39,5
     = 26,3