Let \hat{F}=L(f(t)) be the Laplace transform of f(t). Show that: L(f(at))=\frac{1}{a}\hat{F}(\frac{s}{a})

Lucille Davidson

Lucille Davidson

Answered question

2021-12-08

Let
F^=L(f(t))
be the Laplace transform of f(t). Show that:
L(f(at))=1aF^(sa)

Answer & Explanation

porschomcl

porschomcl

Beginner2021-12-09Added 28 answers

Make a change of variables in the integral. Scale with α :
L(f(at))(s)=0+f(at)estdt={u=at}=1a0+f(u)e(sa)udu=1aL(f(t))(sa)
Bob Huerta

Bob Huerta

Beginner2021-12-10Added 41 answers

Hint: From the definition, L{f(at)} is an improper integral, try this with the sustitution r=at, then
\int_0^{\infty} e^{-st} f(at)dt=\int_0^{\infty} e^{-\frac{s}{a}r} f(r)\frac{1}{a}dr

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