If $\mathcal{L}\{f(t)\}=F(s)$, what is the value of $\mathcal{L}\{f\left(\frac{t}{a}\right)\}$?
Well, I tried the problem and got $$a \, \int_{0}^{\infty} e^{-s a u} \, f(u) \, du$$ using integration by parts. After this I don't know how to proceed. Help would be appreciated.