（3x+1)(x-1)-(x+3)(5x-6)
=3x^2-3x+x-1-(5x^2-6x+15x-18)
=3x^2-3x+x-1-5x^2+6x-15x+18)
=-2x^2-11x+17=x^2-10x+m
m=-3x^2-x+17