（2）用函数解一元二次方程

#include<stdio.h>
#include<math.h>
double x1, x2, disc, p, q;//全局变量
int main()
{
  void jg1(double, double);
  void jg2(double, double);
  void jg3(double, double);
  double a, b, c;
  scanf("%lf%lf%lf", &a, &b, &c);
  disc = b * b - 4 * a * c;
  if (disc > 0)
  {
    jg1(a, b);
    printf("x1=%5lfx2=%5lf", x1, x2);
  }
  if (disc == 0)
  {
    jg2(a, b);
    printf("x1=x2=%5lf", x1);
  }
  if (disc < 0)
  {
    jg3(a, b);
    printf("x1=%lf+%lfi\tx2=%lf-%lfi",p,q,p,q);
  }
  return 0;
}
void jg1(double a, double b)
{
  p = -b / (2 * a); q = sqrt(disc) / (2 * a);
  x1 = p + q; x2 = p - q;
}
void jg2(double a, double b)
{
  p = -b / (2 * a);
  x1 = x2 = p;
}
void jg3(double a, double b)
{
  p = -b / (2 * a); q = sqrt(-disc) /( 2 * a);
}