18/m^2-9+3/3-m
=18/(m-3)(m+3)-3/(m-3)
=18/(m-3)(m+3)-3(m+3)/(m-3)(m+3)
=(18-3(m+3))/(m-3)(m+3)
=(9-3m)/(m-3)(m+3)
=-3/(m+3)