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

int main (void)
{
    int a = 1;
    int b = 2;
    int c = 3;
    double delta;
    double x1;
    double x2;
    delta = b*b - 4*a*c;
    if (delta > 0)
    {
        x1 = (-b + sqrt(delta)) / (2*a);
        x2 = (-b - sqrt(delta)) / (2*a);
        printf("该一元二次方程有两个解, x1=%f, x2=%f\n", x1, x2);
    }
    else if (delta == 0)
    {
        x1 = (-b) / (2*a);
        x2 = x1;
        printf("该一元二次方程有唯一解, x1 = x2 = %f\n", x1);
    }
    else (delta < 0)
    {
        printf("无解\n");
    }
    return 0;
}



错误：   error C2143: syntax error : missing ';' before '{'

else (delta < 0)
    {
        printf("无解\n");
    }
    return 0;
}

//else  后面没有条件  去掉(delta < 0)

else (delta < 0)改成 else if(delta < 0)或者 else

谢谢版主

谢谢