tolong dibantu kawan deretan geometri 2.a=1/2 r= 1/3 s5=

deret geometri tak hingga untuk r<1
Sn = a(1-r^n)/(1-r)
S5 = 1/2 (1-(1/3)^5)/(1-1/3)
      = 1/2 (1- 1/243) / (2/3)
      = 1/2 . 3/2 . (242/243)
      = 3/4 (242/243)
      = 121/162