Hitunglah jumlah deret dari 2+4+8+...+128

dik= deret geometri
U1= a= 2
r= U2/U1
r= 4/2
r= 2

[tex]un = {ar}^{ n - 1} \\ 128 = 2 \times {2}^{n - 1} \\ 64 = {2}^{n - 1} \\ {2}^{6} = {2}^{n - 1} \\ 6 = n - 1 \\ n = 7[/tex]
[tex]sn = \frac{a( {r}^{n} - 1) }{r - 1} \\ s7 = \frac{2( {2}^{7} - 1) }{2 - 1} \\ s7 = 2(128 - 1) \\ s7 = 2(127) \\ s7 = 254 [/tex]