Question

求解一方程 x^2-3x+2-e^x=0 用C++

如题，主要是 e^x 不会，最好能用迭代法来求解，谢谢

Answer 1

参考
http://zhidao.baidu.com/question/39397721.html

针对x^2-3x+2-e^x=0

#include <stdio.h>
#include <math.h>

typedef double (*Fun)(double);

double secant (double x0, double x1, Fun f) //割线法
{
double f0, f1, x2;
f0 = f(x0); f1 = f(x1);
x2 = x1 - f1 * (x1 - x0) / (f1 - f0);
while(fabs(x2 - x1) > 1e-12)
{
x0 = x1, f0 = f1;
x1 = x2, f1 = f(x1);
x2 = x1 - f1 * (x1 - x0) / (f1 - f0);
}
return x2;
}

double fun(double x) //f(x)=x^2-3x+2-e^x
{
return x * (x - 3.0) + 2.0 - exp(x);
}

int main(void)
{
double ret = secant(1.0, 2.0, fun);
printf("f(%.10f) = %.10f\n", ret, fun(ret));
return 0;
}

结果：f(0.2575302854) = 0.0000000000