设x+1=y
y^3-6y-4
=y^3+2y^2-2y^2-4y-2y-4
=y^2(y+2)-2y(y+2)-2(y+2)
=(y+2)(y^2-2y-2)
=(y+2){(y-1)^2-3}
=(x+1+2)(x^2-3)
=(x+3)(x^2-3)=0
x=-3 x=±√3