Question 257440
z^2-12z+32/z^2+z-20 
Factor the NUM and DEN
= (z-8)*(z-4)/(z+5)*(z-4)
Both NUM and DEN have (z-4), so cancel them.
= (z-8)/(z+5)
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I don't know what "factors of one" means.  Dividing by one doesn't change anything.