$$ ax^3+bX^2+cx+d=0 $$ 根的关系: $$ x1 + x2 + x3 = (-\frac{b}{a}) $$ $$ x1 \times x2 + x1 \times x3 + x2 \times x3 = \frac{c}{a} $$ $$ x1 \times x2 \times x3 = (-\frac{d}{a}) $$ 牛顿迭代解方程(x0附近的根) double Newton_Iterative(double a,double b,double c,double d,double x0) { double f0,f0d,x; x = x0; do