Calculation with function For as long as I go around it I do not get to anything
If  $\phi \left ( f(x)-1\right )=2x+5$
and
$\phi (x)=2f(x+1)+1$
find $f(4)$

just an attempt
$$\phi (f (x)-1)=2x+5=2f(f (x))+1$$
thus
$$f (f (x))=x+2$$
$$f (4)=f (f (f (f (0)))) $$
