I hope in the near future complex numbers will be added to Moodle Formulas (both the arithmetic and display of complex numbers.)
It takes quite a bit of coding to create a simple problem like
Just the display of the 24 visible complex numbers takes a substantial amount of work, to avoid ugly looking numbers like 0+-2*i ( instead of -2i ) or 1+-1*i ( instead of 1-i ). A poly function would be great here with increasing powers. [ e.g. Poly("i",[-1,1]); gives -i+1 instead ]
Multiplication of 3x3 matrices with 9 numbers, each with a real part and an imaginary part, where all complex multiplications and additions have to be coded in the global variables field is quite a task. (Imagine computing the inverse of a matrix!)
In this problem I precomputed 20 complex 3x3 (nice) matrices with their inverses and entered their real and imaginary parts (all computed and sorted by my TI-Nspire, and copy and pasted into Moodleformulas) This allowed me to get 190 different combinations of bases. Then all matrix computations had to be programmed.
Here is what students enter (algebraic formula fields are used, and partial credit is computed; all real and imaginary entries are integers)
and graded
Of course it may be that I am not familiar with Moodle Formulas features that would simplify all this (I am relatively new to Moodle Formulas ... been using it for 8 months now)