(x-1)(x-2)(x-3)(x-4)-48=((x-1)(x-4))((x-2)(x-3))-48=(x^2-5x+4)(x^2-5x+6)-48=(x^2-5x+4)^2+2(x^2-5x+4)-48=((x^2-5x+4)+8)((x^2-5x+4)-6)=(x^2-5x+12)(x^2-5x-2)
=x^4-10x^3+36x^2-57x-12
