9-a²/a²+6a+9÷a²-3a/a+1/a
=(3-a)(3+a)/(a+3)²÷a²[a-3]/[a²+1]
=(3-a)(3+a)(a²+1)/[(a+3)²a²(a-3)]
=-(a²+1)/[(a+3)a²]