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