m的2次方-9分之12+3-m分之2+m+3分之2
问题描述：
m的2次方-9分之12+3-m分之2+m+3分之2
答
12/(m^2-9)+2/(3-m)+2/(m+3)
=12/(m^2-9)-2/(m-3)+2/(m+3)
=12/(m^2-9)-2(m+3)/(m^2-9)+2(m-3)/(m^2-9)
=[12-2(m+3)+2(m-3)]/(m^2-9)
=(12-2m-6+2m-6)/(m^2-9)
=0.