Problem
ALG-B3-M09-P003 Positivity
#3
★★☆☆☆ Level 2 of 5
Let \(f\) be additive, \(f(x)\ge0\) for \(x>0\), and \(f(1)=6\). Find \(f\).
Positivity gives monotonicity.
If \(x
Sign becomes order.