[tex]\frac{x^2-x-6}{x^2-4}=(*)\\------------\\x^2-x-6=0\\a=1;\ b=-1;\ c=-6\\\Delta=b^2-4ac;\ \Delta=(-1)^2-4\cdot1\cdot(-6)=1+24=25\\\\x_1=\frac{-b-\sqrt\Delta}{2a};\ x_2=\frac{-b+\sqrt\Delta}{2a}\\\\x_1=\frac{1-\sqrt{25}}{2\cdot1}=\frac{1-5}{2}=\frac{-4}{2}=-2\\\\x_2=\frac{1+\sqrt{25}}{2\cdot1}=\frac{1+5}{2}=\frac{6}{2}=3\\\\x^2-x-6=(x+2)(x-3)[/tex]
[tex]---------------------\\x^2-4=x^2-2^2=(x-2)(x+2)\\-------------------\\\\(*)=\frac{(x+2)(x-3)}{(x-2)(x+2)}=\frac{x-3}{x-2}[/tex]