[4/(x+3)] + [(x+5)/(3-x)] get a common denominator of ( x +3) (3 -x) and we have
[ 4 ( 3-x) ] + [(x + 5)(x + 3)] / [ (x + 3) (3 -x) ] simplify
[ 12 - 4x + x^2 + 8x + 15) ] / [ 3x + 9 - x^2 - 3x ] =
[ x^2 + 4x + 27] / [ -x^2 + 9] =
[x^2 + 4x + 27] / [ 9 - x^2]
