Since the factor in the denominator of the expression is a non-repeated irreducible quadratic, the term that factor contributes to the partial fraction form is .
Knowing the original question might shed some light on what you're trying to do and why.
You were asked to show all the work you did. You said in your first post that you got imaginary values but in
"all" the work you show you have not even attempted to solve for A, B, and C.
If you insist upon writing the fractions with linear, complex, denominators, then, yes, you will get imaginary values for B and C. But normally, we don't want that- we want real denominators and real coefficients. Instead try writing the fraction as
as mr fantastic suggests. Putting in three values for s will give 3 equations for real values of A, B, and C.