Question 136596
{{{log(b,(a))-log(b,(c))=log(b,(a/c))}}}, so 


{{{log(2,(4))-log(2,(16))=log(2,(4/16))=log(2,(1/4))}}}


If {{{y=log(b,x)}}}, then {{{b^y=x}}}, so


If {{{y=log(2,(1/4))}}}, then {{{2^y=1/4}}}, but {{{1/4=1/(2^2)=2^(-2)}}} so {{{y=-2}}}