How do I simplify the rational expression -5x^3y / 15xy^3

Question

I also have to state the restrictions on the variables

Answer 1

-5x³y     -1*5*x*x*x*y        -1*5*x*x*x*y      -1*x*x       -x²
------   =   -------------------    =  ------------------  =  --------  =  -----
15xy³     3*5*x*y*y*y          3*5*x*y*y*y       3*y*y       3y²

 

x ≠ 0 and y ≠ 0 (because they both appear in the denominator of the original expression and we can't divide by 0)