Solution of $f(ax+b)=kf(x)$ with $k,a,b$ are real numbers

Question

I'm interest to know the classification of this functional equation :$f(ax+b)=kf(x)$ with $f$ map $\mathbb{R}$ to $ \mathbb{R}$ , and how do i solve it ? with $a, b, k$ are real numbers .

Note: we assume $f(0)=0 $