4、x³-7x-6=x³-3x²+3x²-7x-6=x²(x-3)+(x-3)(3x+2)=(x-3)(x+2)(x+1)
5、x³-48x-7=x³-7x²+7x²-48x-7=x²(x-7)+(x-7)(7x+1)=(x-7)(x²+7x+1)