(x-1)(x-2)(x-3)(x-4)-48 =[(x-1)(x-4)][(x-2)(x-3)] =(x-5x+4)(x-5x+6)-48 =(x-5x)+10(x-5x)+24-48 =(x-5x)+10(x-5x)-24 =(x-5x+12)(x-5x-2）