Need help Simplifying this Equation

[JieXian]

Hi, I've already worked out the question until part (a) but I don't understand how they go from (a) to (b) right at the bottom of the image.

How did they change -s + i to s - i ?

[PLAIN]http://img64.imageshack.us/img64/9366/unledrze.png [Broken]

Thank you very much for your help.

 

[SammyS]

What is -(s - i) ?

 

[JieXian]

What is -(s - i) ?

Sorry to not have specified earlier.

s is a constant (complex argument s for Laplace transform) and i is the imaginary number.

Here's the solutions they provided. I though I should show you the bigger picture.

[PLAIN]http://img36.imageshack.us/img36/7600/captureir.jpg [Broken]

Thank you.

 

[HallsofIvy]

That was not the point! SammyS was trying to get you to see that they went from -s+i to s- i by factoring out a "-1": -(s- i)= -s+ i.

 

[JieXian]

Ok thanks a lot hahahaha I feel so stupid.

Actually I was panicking about the (-s + i)^2 to (s - i)^2 change at the denominator. Now I've just worked it out to be equal...

Thanks a lot.