(x-1)(x-2)(x-3)(x-4)-48
=[(x-4)(x-1)]*[(x-2)(x-3)]-48
=(x²-5x+4)(x²-5x+6)-48
=(x²-5x)²+(4+6)(x²-5x)+4*6-48
=(x²-5x)²+(12-2)(x²-5x)-24
=(x²-5x+12)(x²-5x-2)
系数在有理数范围内,分解到此为止。
下面是局部分解。
①系数在实数范围内,可以继续分解:
x²-5x-2=(x²-5x+2.5²)-(2+2.5²)=(x-2.5)²-8.25
=(x-2.5+根号8.25)(x-2.5-根号8.25)
②系数在复数范围内,可以继续分解:
x²-5x+12=(x²-5x+2.5²)+(12-2.5²)=(x-2.5)²+5.75
=[x-2.5+(根号5.75)i]*[x-2.5-(根号5.75)i]