=(x-1)(x-4)(x-2)(x-3)-48
=(x²-5x+4)(x²-5x+6)-48
=(x²-5x)²+10(x²-5x)-24
=(x²-5x+12)(x²-5x-2)
因式分解：(x-1)(x-2)(x-3)(x-4)-48 (最好用十字相乘)
=(x-1)(x-4)(x-2)(x-3)-48
=(x²-5x+4)(x²-5x+6)-48
=(x²-5x)²+10(x²-5x)-24
=(x²-5x+12)(x²-5x-2)