Inverse Laplace Transform: How to Manipulate Fractions for Completing the Square

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SUMMARY

The discussion focuses on finding the inverse Laplace transform of the function F(s) = (3s + 7) / (s² - 2s + 10). The denominator is manipulated by completing the square to yield F(s) = (3s + 7) / ((s - 1)² + 9). The user identifies that the first fraction can be separated into two parts, allowing for the application of the inverse transform formulas for sine and cosine functions. The key challenge lies in manipulating the first fraction to align with the cosine transform equation, utilizing the shifting theorem for proper adjustment.

PREREQUISITES
  • Understanding of inverse Laplace transforms
  • Familiarity with completing the square technique
  • Knowledge of Laplace transform properties, including shifting theorems
  • Proficiency in manipulating algebraic fractions
NEXT STEPS
  • Study the application of the shifting theorem in Laplace transforms
  • Learn how to manipulate fractions for inverse Laplace transforms
  • Explore the derivation of inverse transforms for e^(at)cos(bt)
  • Practice completing the square with complex numbers in Laplace contexts
USEFUL FOR

Students studying differential equations, engineers applying control theory, and mathematicians working with Laplace transforms.

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Homework Statement


Find the inverse laplace transform of \frac{3s + 7}{s^{2} - 2s + 10}

Homework Equations


completing the square.
e^{at}sin(bt) = \frac{b}{(s-a)^{2} + b^{2}}
e^{at}cos(bt) = \frac{s-a}{(s-a)^{2} + b^{2}}

The Attempt at a Solution


F(s)= \frac{3s + 7}{s^{2} - 2s + 10}
F(s) = \frac{3s + 7}{(s-1)^{2} +9}
F(s) = \frac{3s}{(s-1)^{2} +9} + \frac{7}{(s-1)^{2} +9}

after this i don't know how to manipulate the first fraction to fit the cosine equation. I know the 3 can be taken up front and a=1 and b=3 I am pretty sure when comparing with the cosine equation but there the problem of making s into s-1.
 
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Don't you have the shifting theorems? Like$$
\mathcal L e^{at}f(t) = \mathcal L(f(t))|_{s \to s-a}$$
 

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