Question 156553
[z^2 - 10z+21/z^2 - 13 + 36]/[z^2 -11z + 24/z^2 - 9z + 14]
[(z-7)(z-3)/(z-9)(z-4)]/[(z-8)(z-3)/(z-7)(z-2)]
[(z-7)(z-3)/(z-9)(z-4)]*[z-7)(z-2)/(z-8)(z-3)]
[(z-7)(z-7)(z-2)]/[(z-9)(z-4)(z-8)]