7 log 1/49 x 7 log 3 x 3 log 5 =

7 log 1/49 x 7 log 3 x 3 log 5 =
= 7 log 7^-2 x 7 log 5
= -2 x 7log5

7 log (7 pangkat -2) x 7 log 5 = -2 x 7 log 7 x 7 log 5 = – 2 x 7 log 5 = 7 log 1/25