jumlah 50 suku pertama deret log5+log55+log605+log6655+.... adalah...

= log 5 + log 5.11 + log 5.11²+ log 5.11³ + log 5.11⁴..
= log 5 + (log 5 + log 11) + (log 5 + log 11²) + (log 5 + log 11³) + (log 5+log 11⁴)..
= log 5 + log 5 + log 5 + log 5 + log 5 + log 11 + 2 log 11 + 3 Log 11 + 4 log 11
= 4 log 5 + 10 log 11

Log 5 --> S1 = 1
                S2 = 2
               S50 = 50  --> S50 utk log 5  = 50 log 5


Log 11 --> u1 = 0
                 u2 = 1  --> s2 = 1
                 u3 = 2  --> s3 = 3
                 u4 = 3 -->  s4 = 6
                 u5 = 4 ---> s5 = 10
                u50 = 49  --> s50 = 1/2 n (a+u50)
                                            = 1/2. 50 (0+49)
                                            = 1225  ----> S50 utk log 11 = 1225 log 11

S50 = 50 log 5 + 1225 log 11