[编程入门]自定义函数求一元二次方程-题解（C语言代码）

解题思路:
根据Δ大小分类讨论，用求根公式
注意事项:
虚数i手加
参考代码:

#include<stdio.h>

#include<math.h>

void do1(int a,int b,int c)

{

float d,e;

d = b*b*1.0-4*a*c;

e = -b*1.0/(2*a);

printf("x1=%.3f ",e+sqrt(d)/(a*2));

printf("x2=%.3f",e-sqrt(d)/(a*2));

}

void do2(int a,int b,int c)

{

float d,e;

d = b*b*1.0-4*a*c;

e = -b*1.0/(2*a);

printf("x1=x2=%.3f",e);

}

void do3(int a,int b,int c)

{

float d,e;

d = b*b*1.0-4*a*c;

e = -b*1.0/(2*a);

printf("x1=%.3f+%.3fi ",e,sqrt(-d)/(a*2));

printf("x2=%.3f-%.3fi",e,sqrt(-d)/(a*2));

}

int main()

{

int a,b,c;

float d,e;

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

d = b*b*1.0-4*a*c;

e = -b*1.0/(2*a);

if(d>0)

{

do1(a,b,c);

}

if(d == 0)

{

do2(a,b,c);

}

    if(d<0)

{

do3(a,b,c);

}

}