0
$\begingroup$

Image 1

Image 2

How does $-(s^2 + 4) - (2s^2) = (s^2 - 4)$? I have tried different methods to get the result. However, I cannot figure it out.

This is taken out of uni notes in a Laplace Transform question.

Thank you in advance.

P.S: Could be something pretty simple but it seems to be slipping my mind.

  • 3
    The image and text do not agree. The image has: $$-\left[ (s^2+4)-(2s^2)\right]=-(s^2+4)+2s^2$$ – 2017-01-03

1 Answers 1

1

What you have is:

$$-\frac{(s^2+4)-(2s^2)}{(s^2+4)^2}=\frac{-(s^2+4)+(2s^2)}{(s^2+4)^2}=\frac{-s^2-4+2s^2}{(s^2+4)^2}=\frac{s^2-4}{(s^2+4)^2}$$

  • 0
    thank you very much, as i suspected pretty simple just been looking at it for too long – 2017-01-03
  • 0
    you are very welcome! – 2017-01-03