编写题解 1028: [编程入门]自定义函数求一元二次方程

解题思路:

注意事项:

参考代码:

//求方程 的根，用三个函数分别求当b^2-4ac大于0、等于0、和小于0时的根，并输出结果。从主函数输入a、b、c的值。

#include<stdio.h>

#include<math.h>

int main()

{

void p(double a,double b,double c);

void q(double a,double b,double c);

void f(double a,double b,double c);

double a,b,c;

scanf("%lf %lf %lf",&a,&b,&c);

if(b*b-4*a*c>0) p(a,b,c);

if(b*b-4*a*c==0) q(a,b,c);

if(b*b-4*a*c<0) f(a,b,c);

return 0;

} 

void p(double a,double b,double c)

{

printf("x1=%.3lf x2=%.3lf\n",(-b+sqrt(b*b-4*a*c))/2/a,(-b-sqrt(b*b-4*a*c))/2/a);

}

void q(double a,double b,double c)

{

printf("x1=%.3lf x2=%.3lf\n",-b/2/a,-b/2/a);

}

void f(double a,double b,double c)

{

printf("x1=%.3lf+%.3lfi x2=%.3lf-%.3lfi\n",-b/(2*a),sqrt(4*a*c-b*b)/(2*a),-b/(2*a),sqrt(4*a*c-b*b)/(2*a));

}