suatu barisan geometri U2=6 dan U5=48. jumlahkan 7 suku pertama barisan tersebut adalah.... A.189 B.193 C.381 D.384 tolong donk jawabkan pertanyaanku besok kal

U2 = ar = 6
U5 = ar⁴ = 48
         ar . r³ = 48
           6 r³ = 48
              r³ = 48/6
              r³ = 8
              r = 2
           ar = 6
           a . 2 = 6
               a=  6/2
               a = 3
Sn = a (rⁿ - 1) / ( r - 1)
S7 = 3 (2⁷ - 1) / (2 - 1)
      = 3 (128 - 1) / 1
      = 3 . 127
      = 381 (c)