[MATLAB基础] 符号解三次方程有误？

[zsy312]

syms x
s=solve(x^3+3*x-1,x);
s=real(s)+1i*imag(s)
ds=double(s)

输出：

s =
 
                                                                1/2*(4+4*5^(1/2))^(1/3)-2/(4+4*5^(1/2))^(1/3)
 -1/4*(4+4*5^(1/2))^(1/3)+1/(4+4*5^(1/2))^(1/3)+1/2*i*3^(1/2)*(1/2*(4+4*5^(1/2))^(1/3)+2/(4+4*5^(1/2))^(1/3))
 -1/4*(4+4*5^(1/2))^(1/3)+1/(4+4*5^(1/2))^(1/3)-1/2*i*3^(1/2)*(1/2*(4+4*5^(1/2))^(1/3)+2/(4+4*5^(1/2))^(1/3))
 
 

ds =

   0.3222          
  -0.1611 + 1.7544i
  -0.1611 - 1.7544i