一道一元三次方程
问题描述：
一道一元三次方程
求方程x^3-x-2=0的解
答
近似解为：
-0.7607 + 0.8579i
-0.7607 - 0.8579i
1.5214
精确解为：
1/3*(27+3*78^(1/2))^(1/3)+1/(27+3*78^(1/2))^(1/3)
-1/6*(27+3*78^(1/2))^(1/3)-1/2/(27+3*78^(1/2))^(1/3)+1/2*i*3^(1/2)*(1/3*(27+3*78^(1/2))^(1/3)-1/(27+3*78^(1/2))^(1/3))
-1/6*(27+3*78^(1/2))^(1/3)-1/2/(27+3*78^(1/2))^(1/3)-1/2*i*3^(1/2)*(1/3*(27+3*78^(1/2))^(1/3)-1/(27+3*78^(1/2))^(1/3))