Hi all, I am a bit rusty and have hit a snag with decomposition of partial fractions, I am taking an Engineering course dealing with Laplace transforms. The example is: F(s)= 3 / s(s2+2s+5) Now I get that there are complex roots in the denominator and that there are conjugate complex roots (s+1±2i) giving: F(s)= 3 / s(s+1-2i)(s+1-2i) So partial fraction decomposition would give: F(s) = K1/s + K2/(s+1+2i) + K3/(s+1-2i) Ok, so solving for K1= 3/5 is easy and I get that, but when it comes to K2 which involves substituting (-1-2i) in for 's' and then expanding, I can't seem to get the answer. What I did was: K2=3[STRIKE](s+1+2i)[/STRIKE]/s(s+1-2i)[STRIKE](s+1+2i)[/STRIKE] K2=3/s(s+1-2i) K2=3/(-1-2i)[(-1-2i)+1-2i)] It is the algebraic expansion on the denominator that is getting me. When I do it I get: (-1-2i)[(-1-2i)+1-2i)] = (-1-2i)(0-4i) =-1(-4i)-2i(-4i) =4i+8i2 =8+4i =4(2+i) However my textbook gets -3/20 (2+i) for the final partial fraction... I'm lost any help would be greatly appreciated.