Matrix in SymbolicUtils?

[tomtom]

good for you to be so helpful

so I ask more questions now:

1. how to declare a symbolic complex number in the form of x = a + jb and x = rcosθ + jrsinθ? that is, x,a,b,r,θ are all symbols.
2. in the following, how do I arrange p as a polynomial in L?
3. then, how to get the coefficients of the polynomials?
4. in general, how do I manipulate a SymbolicUtils.Term object? should I transform it into a standard Julia expression (how?) and then transverse the expression tree?

julia> @syms L α₁ α₂
(L, α₁, α₂)

julia> p = (1 - L) * (1 - α₁ * L) * (1 - α₂ * L)
(1 + (-1 * L)) * (1 + (-1 * L * α₁)) * (1 + (-1 * L * α₂))

many thanks!