# The concept of generalised functions (distributions) and derivatives

Desvl at
IntroductionTo begin with we consider a calculus problem that you may have seen in your exam:Let $$f$$ be a continuous function on $$[0,\infty)$$ that $$\lim_{x \to \infty} f(x)=l$$. Prove that $\int_0^\infty \frac{f(ax)-f(bx)}{x}\mathrm{d}x = (f(0)-l)\ln\frac{b}{a}$And we solve this problem as fo……