(ax+2)(ax-1)-x(x-3)
=a^2x^2+ax-2-x^2+3x
=(a^2-1)x^2+(a+3)x-2
=(a+1)(a-1)x^2+(a+3)x-2
=((a+1)x-1)((a-1)x+2)
=(ax+x-1)(ax-x+2)