2a/a^2-9-1/3+a

问题描述:

2a/a^2-9-1/3+a

2a/(a²-9)-1/(3+a)
=2a/[(a+3)(a-3)]-1/(a+3)
=(2a-a+3)/[(a+3)(a-3)]
=(a+3)/[(a+3)(a-3)]
=1/(a-3)