Dividing complex numbers

4-2i/3+1

was expecting a complex number in the denominator.

I will assume you meant:
(4-2i)/(3+i)
= (4-2i)/(3+i)*(3-i)/(3-i)
= (12 - 4i - 6i + 2i^2)/(9 - i^2)
= (10 - 10i)/(9+1)
= 1 - i