error C2143: 语法错误 : 缺少“;”(在“{”的前面

# include <stdio.h>
# include <math.h>
int main(void)
{
int a = 4 ;
int b = 5 ;
int c = 9 ;
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("x1 = %f, x2 = %f\n",x1 ,x2) ;
}
else if (delta == 0)
{
x1 = (-b) / (2*a) ;
x2 = x1 ;
printf("x1 = x2 = %f\n",x1) ;
}
else (delta < 0)
{ //error C2143: 语法错误 : 缺少“;”(在“{”的前面
printf("无解\n") ;
}
return 0 ;
}

---

# include <stdio.h>
# include <math.h>
int main(void)
{
int a = 4 ;
int b = 5 ;
int c = 9 ;
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("粗亮x1 = %f, x2 = %f\n",x1 ,x2) ;
}
else if (delta == 0)
{
x1 = (-b) / (2*a);
x2 = x1;
printf("x1 = x2 = %f\岩森宽n",x1) ;
}
else if(delta < 0) //这里如果没有IF的话esle是不能跟条件的
{ //error C2143: 语法错春空误 : 缺少“;”(在“{”的前面
printf("无解\n") ;
}
return 0 ;
}

---

delta = b*b - 4*a*c ;
if (delta > 0)
{
x1 = (-b + sqrt(delta)) / (2*a) ;
x2 = (-b - sqrt(delta)) /茄孙 (2*a) ;
printf("x1 = %f, x2 = %f\n",x1 ,x2) ;
}

这一段里的printf("x1 = %f, x2 = %f\颤坦链n",x1 ,x2) ;这一信神句，你没加双引号。应该这样：
printf("x1 = %f, x2 = %f\n",x1 ,x2”)；

---

else
{
printf("无解\n") ;
}

---

else (delta < 0)这儿少了if
如果袜历没有if，else之后将（）里的内容认告乱搜为是一个陪郑语句，不是判断条件
去掉 (delta < 0)或者在else后加个if ：else if(delta < 0)

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