let $f(x)$ such $$f'(x)=f\left(x+\dfrac{1}{e}\right)$$
I found this problem one solution(maybe have other)
Let $f(x)=ae^{bx}$ then we have $$abe^{bx}=ae^{bx+\dfrac{b}{e}}\Longrightarrow ae^{bx}(b-e^{b/e})\Longrightarrow b=e$$ so $$y=ae^{ex}$$ is one solution? and How find other solution? Thank you