partial fractions (1 Viewer)

[SofaKingGreat]

s^2/(s+1)^3

How do you do that? I have tried it a couple of times and come up with answers that dont revert back to that if i get a common denominator again. If someone could help me out it would be great. Thanks.

 

[Xayma]

What exactly do you want to do with it? Make it simpler, or what?

 

[SofaKingGreat]

expand it into its partial fractions A/(s+1) etc.

 

[KeypadSDM]

Lol, I've forgotten how to do it when there's square or plus factors on the bottom.

 

[Heinz]

s^2/(s+1)^3 = a/s+1 + b/(s+1)^2 + c/(s+1)^3

s^2 = a(s+1)^2 + b(s+1) + c

@ s = 0, LHS = 0, RHS = a + b + c
@ s = -1, LHS = 1, RHS = c
:. c = 1
@ s =1, LHS = 1, RHS = 4a + 2b +c

4a+2b = 0 and a+b = -1, solve simultaneously to get a = 1, b = -2 and c you already have

:. s^2/(s+1)^3 = 1/s+1 - 2/(s+1)^2 + 1/(s+1)^3

 

[SofaKingGreat]

thankyou. i was making a very silly error.