Question

show that f°f=2f

f=x+1

Answer 1

$f(x)=x+1$. The composition $f\circ f$ has the form: $f\circ f(x)=f(x+1)=x+2$;

$2f(x)=2x+2$. As we can see, $f\circ f(x)\neq2f(x)$.