Question

f(2x)=Inx.求f(x)的导数

Answer 1

令t=2x,则 x=t/2

所以有 f(2x)=f(t) = ln(t/2)

故有 f(x)=ln(x/2)

所以 f'(x)=(ln(x/2))'

=1/(x/2) * (x/2)'

=2/x * 1/2 =1/x