Question 72423
{{{f(2x)=4/(2+x)}}}


Let {{{z = 2x}}}.
Then, {{{x = z/2}}}.


So, {{{f(z)=4/(2+z/2)}}}
or {{{f(z)=8/(4+z)}}}


Replacing z by x
{{{f(x)=8/(4+x)}}}
So, {{{2f(x)=2*8/(4+x)=16/(4+x)}}}