Answer :
factor the numerator and denominator
(x^2-x-6)/(x^2-4)
((x-3)(x+2))/((x+2)(x-2)) the (x+2)'s cancel out leaving...
(x-3)/(x-2)
(x^2-x-6)/(x^2-4)
((x-3)(x+2))/((x+2)(x-2)) the (x+2)'s cancel out leaving...
(x-3)/(x-2)