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