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Guest ExtremeFusion

Inverse Laplace Transform

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Guest ExtremeFusion

Hi guys, does anybody here knows ** to do inverse Laplace?

This three problem (attached) is troubling me for the past few days..

Can somebody please help me in solving this and can you please provide a solution on how you come up with such answer..

Thank you..

BTW, If i don't answer this by April 6, 2008... my professor is gonna cancel my candidacy for graduation..

So please somebody help..

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Guest ExtremeFusion

So am I, aside from the fact that I won't graduate if I don't answer those questions..

BTW, those are from Advance Engineering Math with Numerical Methods subject...troublesome!

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Guest ExtremeFusion

my answer in number 2 is..

-(1/5) + (6/5)e^(-5t)

for number 3

-(3/2)e^(t) + (1/6)e^(-t) + (4/3)e^(2t)

for number 1

i have a partial answer, but i got troubled  on one part, so i cnt gve an answer il try tom.

Thanks mapuamj...

i see you got an interesting input... but how did you come up with those answers?

checking on my notes.. problem 1 is solve by theorem 2 in inverse laplace transform, by which it must be in the form f(s-a), then solve its laplace..

yes i do have answer for that.. i'll post it later and my point why i still post that problem regarding i already have an answer for it...

i'd like to see your solution for both of your answer, its puzzling me..

the third problem is solve by partial fractions, but first you have to get the factor of the polynomial in the denominator.. either by synthetic division or trial and error...

considering synthetic division, i always arrive in a solutiuon that involves imaginary numbers...

and even if I use Casio FX-991 ES calculator to solve its factor, it always arrived at factors containing imaginary numbers...

But my professor says it doesn't have one, or at least the paper that he checked already has no imaginary number on it.. and it is correct..

i'll try posting the "correct" answer on number 1 and number 3.. a little later...

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Guest ExtremeFusion

P.U.P. Manila, btw.. I maybe wrong but when i tried multiplying (s-1)(s-2)(s+1)

i arrived at s^3 - 2s^2 - s + 2...

but from the given problem it is s^3 + 2s^2 -s + 2

they are different in sign.. that is why i always came up with imaginary numbers...

Thanks for number two it is solve by partial fractions.. now i get it..

BTW, please save my butt on question 1 and 3..

I also arrived at factors (s-1)(s+1)(s-2).. like what i have said before when you multiply those factors, the answer is not the same as what is in the problem... puzzling...

and to those out there who have a taste for math, please help me...

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Guest ExtremeFusion

yes i am very sure that this is the denominator in problem three;

s^3 + 2s^2 - s + 2

program? what program? by that you mean our curriculum?

if yes, then we use 2001 Curriculum....

and while you're at it.. can you please check my solution to this question.. i forgot my differential calculus already.. hehehe...

thanks a lot, you are such a big help..

checkthispl0.jpg

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ah gets. .. this is our second to the last lesson on differential equations, "transforms of derivatives" i dont knw if i cn still remember this one.. haha this was taught 2 or 3 yrs ago to us at the latter part of the term so probably im not listening..ahhaha :2funny:

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Guest ExtremeFusion

@mapuamj,

I'm taking BS Mechanical Engineering...

BTW, is it possible that my professor did a typo in the sign of his problem in question number three.. no matter how i figure it out, it always comes to that s^3 + 2s^2 - s + 2 must be s^3 - 2s^2 - s + 2, what do you think?

In case that problem three is not a typo, I've search about Laplace and Inverse Laplace over the net, but i can't see a Laplace that has an imaginary function except for complex conjugate.. involving sin and cos..

If I solve the factors of s^3 + 2s^2 - s + 2, it always has an imaginary number..., that is why i have too look over the net if there are functions of laplace involving imaginary numbers...

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ah..  im not really sure, but base on may notes, thats how we solve that problem, can you consult your professor about that? i really chekd it and there's no possible way on how "i" can get the roots of that if it iss^3 + 2s^2 - s + 2 ... hehe , if you want check out my notes i'l scan it, whats ur ym?

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