Question 126
Show that for positive integers $n_{1}$, $n_{2}$ and $d$,
$$
f\left(n_{1} n_{2}, d\right) \leq f\left(n_{1}, d\right)+n_{1}\left(f\left(n_{2}, d\right)-1\right)
$$
$$
f\left(n_{1} n_{2}, d\right) \leq f\left(n_{1}, d\right)+n_{1}\left(f\left(n_{2}, d\right)-1\right)
$$