x²+3x²-4x-12/(x-2)(x+3)

x^2+3x^2-4x-12/(x-2)(x+3)

x^2+3x^2-4x-12/(x^2+3x-2x-6)

x^2+3x^2-4x-12/x^2+x-6

3x^2-3x-2=0

D=b^2-4ac=9-4*3*(-2)=9+24=33

x1=(3+33)/6=36/6=6

x2=(3-33)/6=-30/6=-5