If log72=m, then log4928 is equal to
2(1+2m)
1+2m2
21+2m
1+m
log4928=log 28log 49=log 7+log 42 log 7
=log 72 log 7+log 42 log 7=12+12 log74
=12+12.2 log72=12+log72=12+m=1+2m2