Frustrated with Inverse Laplace Transform: Help Needed!

Kruum
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Homework Statement



This isn't a homework, I'm just trying to recap for a mid-term. Anyways, it's about inverse Laplace transformation and this crap is starting to piss me off! How the heck are you supposed to go from \frac{ \frac{-U}{s}}{R+sL+ \frac{1}{sC}} to - \frac{2 \sqrt{10}}{ \sqrt{15}}e^{-125t}sin(125 \sqrt{15})?

Homework Equations



The values are: U= \sqrt{10}, R=1, L=4*10^{-3}, C=1*10^{-3}

The Attempt at a Solution



My best attempt so far has gotten me to \frac{-U}{s^2+s(R/L)+(1/LC)}=\frac{- \sqrt{10}}{125 \sqrt{15}} \frac{125 \sqrt{15}}{(s+125)^2+(125 \sqrt{15})^2}. I know this is pretty close but not close enough...
 
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I found it out myself. Instead of \frac{-U}{s^2+s(R/L)+(1/LC)} I should have had \frac{-U/LC}{s^2+s(R/L)+(1/LC)}. This gives me the right answer.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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