Series[(1/(1-1.3 B + 0.4 (B^2))),{B,0,5}]

Expand[ (1- 1.3 B + 0.4 (B^2))(1-1.3 (B^(-1))+0.4 (B^(-2)))]

Series[((1-1.3 B+0.4 (B^2))/(1-0.5 B)),{B,0,100}]

((1-(13/10) B+(2/5) (B^2))/(1-(1/2) B))//Simplify

Expand[(1-0.8 B)(1-0.8 (B^(-1)))]

prob38Sol=NSolve[1-0.82 B-0.22 (B^2)+0.28 (B^4)==0,B]

{(1/B),(1/(Abs[B]))}/.prob38Sol

Abs[B]/.prob38Sol