limit, help.

  ( (4 / x^2 - 2x -3 ) - ( 5 / x^2 - x - 6))    factor the denominators

4 / [ (x - 3)(x + 1) - 5 / [ (x - 3)(x +2 )]   =     factor out  [ 1/ (x - 3) ]

[1/(x - 3)]  *  [ 4/ (x + 1) -  (5 (x + 2) ] =     get common denominators

[ 1 /(x - 3 ) ]  * [ 4(x + 2) - 5(x + 1)] / [(x + 1) (x + 2)]  =

[1/(x - 3)] [ - x + 3] /[(x + 1)(x + 2)]  =

[1/ (x -3)] [ - (x - 3)] /  [ (x + 1) (x + 2)]  =

-1 / [(x + 1) ( x + 2)]       take the limit as x → 3    and we have

-1 /[(4)(5)] =

-1/20