Question

What is the laplace transform of 9t^(-9) ?

Answer 1

were you provided a table?

Answer 2

ahm i lost it haha. but i think: is this one?

Answer 3

@inkyvoyd

Answer 4

that's for the positive exponents... I'm not sure you can even use the gamma function to extrapolate the negative factorial here

Answer 5

try evaluating the integral by definition.

Answer 6

whew i forgot calculus i'm sorry can you help me remember that? i'm so sorry

Answer 7

the answer in my notes is -9/s^(-8) . i don't know how that happened :(

Answer 8

if you're taking ODEs and you forgot calculus you're screwed anyways lol

Answer 9

you're arrogant.

Answer 10

I mean, if you're taking physics and you forget calculus you're screwed anyways lol...
I might be arrogant, but unfortunately for you pointing that out doesn't change the fact that if you forgot calculus you're screwed lol.

Just put down the formula for laplace, and we'll evaluate the integral and see where it came from lol.

Answer 11

\(\Huge \int_0^\infty f(t)e^{-st}dt\)
plug in f(t) and let's go.

Answer 12

\[\int\limits_{0}^{\infty} 9t ^{-9} e ^{-st}dt\] ? ?

Answer 13

yeah

Answer 14

of course the hard part now is evaluating that sucker, but i'm sure we'll find a way

Answer 15

?

Answer 16

but p is negative

Answer 17

yeah we have a big problem here because the gamma function isn't defined for negative integers

Answer 18

You can evaluate that integral using integration by parts

Answer 19

You can't evaluate the integral that we posted lol. I checked already; it's a dead end.

Answer 20

Yeah lol i tried it didn't work

Answer 21

It's because the integral doesn't actually exist lol
http://math.stackexchange.com/questions/147126/laplace-transform-of-1-t

Answer 22

I don't know how your notebook has -9/s^(-8) becauese I'm pretty sure it's just wrong

Answer 23

oh, thanks . ya my prof is not really that good in math that's what he said. thanks for your time

Answer 24

scratch that; it's definitely wrong. Here's the inverse laplace of what you have in your notebook.

http://www.wolframalpha.com/input/?i=inverse+laplace&rawformassumption=%7B%22F%22,+%22InverseLaplaceTransformCalculator%22,+%22transformfunction%22%7D+-%3E%22-9%2Fs%5E-8%22&rawformassumption=%7B%22F%22,+%22InverseLaplaceTransformCalculator%22,+%22variable1%22%7D+-%3E%22s%22&rawformassumption=%7B%22F%22,+%22InverseLaplaceTransformCalculator%22,+%22variable2%22%7D+-%3E%22t%22

Someone's just giving you wrong answers lol

Answer 25

wait what? inverse laplace? haha ok i get it now