Hoặc
b) 12x2−9−2x−3;
b) 12x2−9−2x−3=12(x+3)(x−3)−2x−3
=12(x+3)(x−3)−2(x+3)(x+3)(x−3)=12−2(x+3)(x+3)(x−3)
=12−2x−6(x+3)(x−3)=6−2x(x+3)(x−3)