[(x-3)/(x²+6x+9)]+[x/(9-x²)]
=[(x-3)/(x+3）^2]+[x/(3-x)(3+x)]
=[(x-3)^2/(x-3)(x+3)^2]-[x(3+x)/(x-3)(3+x)^2]
=((x-3)^2-x(3+x))/[(x-3)(3+x)^2]
=(x^2-6x+9-3x-x^2)/[(x-3)(3+x)^2]
=9(1-x)/[(x-3)(3+x)^2]