Access to System.Numerics?

As the title asks, do we have access to System.Numerics in the PB? And if not, can we get it? And if not, why not?

Reason for asking - I'm trying to program the solutions for Cubic and Quartic solutions, but nearly all the methods (the easiest ones to code, certainly) require the use of imaginary numbers to find the roots.

If we can't get it, does anyone know of another way to use imaginary numbers (i) in code?

Thanks!