Question

divide : 4z²+6z²-z by -½z

Answer 1

Take z common in the divided and cancel it by the z of divisor, add the left terms of dividend then the resultant would be,
4z+6z-1/-1/2
-(10z-1(2))
-20z-2
It's the quotient and 0 is remainder.

Answer 2

I think it should be solved like that:
4z+6z-1/-1/2
-(10z-1(2))
-20z-2

It's quotient will be 0. Hope it will help you.