hey

im stuggling on a question, can someone please help

how do you get from
x(t) = e^(-t/3)u(t)
to
X(s) = 3/(3s + 1)
x

Question

hey

im stuggling on a question, can someone please help

how do you get from
x(t) = e^(-t/3)u(t)
to
X(s) = 3/(3s + 1)
x

anonymous · Answer

laplace transform?

anonymous · Answer

yeah but can not seem to get the answer. Help? I am really struggling x

anonymous · Answer

$$\large{L(e^{-{\frac{t}{3}}}u(t))= \frac{1}{s+\frac{1}{3}}}= \frac{3}{3s+1}$$

amistre64 · Answer

hmm, not to adept with these, but it looks like maybe:
$$-\frac{1}{3}t-st=-t(s+\frac{1}{3})$$
how you get to Lanas I aint got no clue :)

but afterwards you can simplify it by mutliplying at all by 3/3

anonymous · Answer

but u cant have t's in X(s)?

amistre64 · Answer

right, which is the part im not to adept at ;)

anonymous · Answer

How would you show this from first principles?
x

amistre64 · Answer

ack!!

amistre64 · Answer

pauls online notes has some good material

anonymous · Answer

im not sure i did it right either, what i did was laplace(e^(-t/3)) ...

amistre64 · Answer

http://tutorial.math.lamar.edu/Classes/DE/LaplaceDefinition.aspx

anonymous · Answer

$$e^{-\alpha t}u(t)= \frac{1}{s+ \alpha}$$