# include <stdio.h>
# include <math.h>
int main (void)
{
    double a,b,c,x1,x2,delta;
    printf("请输入系数a= ")；
        scanf("%lf",&a);
    printf("请输入系数b= ")；
        scanf("%lf",&b);
    printf("请输入系数c= ")；
        scanf("%lf",&c);
   
    delta = b * b - 4 * a * c;
   
    do
    {
        
        
        if (b*b-4*a*c>0)
        {
            x1=(-b + sqrt(delta)) / (2 * a);
            x2=(-b - sqrt(delta)) / (2 * a);
            printf("有两个解x1=%lf,x2=%lf/n",x1,x2);
        }
        if else (b*b-4*a*c==0)
        {
            x1=(-b)/(2*a)
            printf("有唯一解x1=x2=%lf/n",x1);
        }
        else
        {
            printf("无解/n")；
        }        
    }    while(1);
               
    return 0;
}


--------------------Configuration: 一元二次方程 - Win32 Debug--------------------
Compiling...
一元二次方程.cpp
F:\c\一元二次方程.cpp(6) : error C2018: unknown character '0xa3'
F:\c\一元二次方程.cpp(6) : error C2018: unknown character '0xbb'
F:\c\一元二次方程.cpp(7) : error C2146: syntax error : missing ';' before identifier 'scanf'
F:\c\一元二次方程.cpp(8) : error C2018: unknown character '0xa3'
F:\c\一元二次方程.cpp(8) : error C2018: unknown character '0xbb'
F:\c\一元二次方程.cpp(9) : error C2146: syntax error : missing ';' before identifier 'scanf'
F:\c\一元二次方程.cpp(10) : error C2018: unknown character '0xa3'
F:\c\一元二次方程.cpp(10) : error C2018: unknown character '0xbb'
F:\c\一元二次方程.cpp(11) : error C2146: syntax error : missing ';' before identifier 'scanf'
F:\c\一元二次方程.cpp(25) : error C2059: syntax error : 'else'
F:\c\一元二次方程.cpp(26) : error C2143: syntax error : missing ';' before '{'
F:\c\一元二次方程.cpp(28) : error C2146: syntax error : missing ';' before identifier 'printf'
F:\c\一元二次方程.cpp(30) : error C2181: illegal else without matching if
F:\c\一元二次方程.cpp(32) : error C2018: unknown character '0xa3'
F:\c\一元二次方程.cpp(32) : error C2018: unknown character '0xbb'
F:\c\一元二次方程.cpp(33) : error C2143: syntax error : missing ';' before '}'
执行 cl.exe 时出错.

一元二次方程.obj - 1 error(s), 0 warning(s)



没搞明白，怎么错那么多？又查不出来

不要用中文分号     还有是else if   不是if else

[ 本帖最后由 qq923503779 于 2013-7-25 14:59 编辑 ]

# include <stdio.h>
# include <math.h>
int main (void)
{
    double a,b,c,x1,x2,delta;
    printf("请输入系数a= ");
        scanf("%lf",&a);
    printf("请输入系数b= ");
        scanf("%lf",&b);
    printf("请输入系数c= ");
        scanf("%lf",&c);
   
    delta = b * b - 4 * a * c;
   

        
        
        if (b*b-4*a*c>0)
        {
            x1=(-b + sqrt(delta)) / (2 * a);
            x2=(-b - sqrt(delta)) / (2 * a);
            printf("有两个解x1=%lf,x2=%lf/n",x1,x2);
        }
         else if (b*b-4*a*c==0)//是else if
        {
            x1=(-b)/(2*a);//缺分号
            printf("有唯一解x1=x2=%lf/n",x1);
        }
        else
        {
            printf("无解\n");//是\n不是/n
        }        
   
               
    return 0;
}
 把do{}while(1);死循环去掉......

[ 本帖最后由 蔡梓锋 于 2013-7-25 10:09 编辑 ]

用if都能解决问题了，干嘛要循环

我写死循环是为了，可以多次计算。而不用退出重开