Question

Tolong bantuin
1.barisan geometri u5 = 3 dan u9 = 768
tentukan :
a.r ( rasio )
b. s5

Answer 1

U9= ar^5 = 768
u5 = ar^4 = 3

r^4 = 768/3 = 256
a.  r = 4

ar^4 = 3
a * 256 = 3
a = 3/256

b. S5 = a ( r^5 - 1) / ( r-1)
         = 3/256 ( 4^5 -1) / (4-1)
        = 3/256 (1.024 -1) / 3
        = 1 / 256 (1023)
       = 1023/256
    S5 = 4