Question

解方程x^3+3x^2-3x-1=0.多谢!

Answer 1

x^3+3x^2-3x-1=0

(x^3-1)+3(x^2-x)=0

(x-1)(x^2+x+1)+(x-1)*3x=0

(x-1)(x^2+4x+1)=0

x1=1

x2=-2+根号3

x3=-2-根号3

解x^2+4x+1=0,利用求根公式

x1=-b/2a+根号下(b^2-4ac)

x2=-b/2a-根号下(b^2-4ac