一元二次方程与一元二次函数

My_A

做了个计算 一元二次方程和一元二次函数顶点与顶点式 的程序，希望大家多多指教

1. #include <stdio.h>
   
2. #include <math.h>
   
3. 
   
4. #define NOT_ZERO(x) if((x)==0.0){return 0;}                // 二次方程的二次项系数不为0
   
5. #define SQUARE(x) ((x)*(x))
   
6. #define ANSWER(a,b,c,x) ((a)*SQUARE(x) + (b)*(x) + (c))    // 算方程结果
   
7. #define MAX_Y(a,b) ((-(b))/(2*(a)))                        // 算最大/最小值
   
8. 
   
9. typedef  struct{ double x,y; } POINT,*pPOINT;
   
10. 
    
11. typedef struct{ double x1,x2; } ANSWER_X,*pANSWER_X;
    
12. 
    
13. typedef struct{ double a,h,k; } VERTEX_TYPE,*pVERTEX_TYPE;
    
14. 
    
15. // 解方程
    
16. int solute(double a,double b,double c,pANSWER_X answer)
    
17. {
    
18.     NOT_ZERO(a);
    
19. 
    
20.     double delta = SQUARE(b)-(4*a*c);
    
21. 
    
22.     // 判断根的情况
    
23.     if(delta >= 0.0){
    
24.         if(delta > 0){
    
25.             answer->x1 = (-b+sqrt(delta))/(2*a);
    
26.             answer->x2 = (-b-sqrt(delta))/(2*a);
    
27.         }else {
    
28.             answer->x1 = answer->x2 = MAX_Y(a,b);
    
29.         }
    
30. 
    
31.         return 1;
    
32.     }else{
    
33.         return 0;        // 无实数根
    
34.     }
    
35. }
    
36. 
    
37. // 计算顶点坐标
    
38. int vertex(double a,double b,double c,pPOINT answer)
    
39. {
    
40.     NOT_ZERO(a);
    
41. 
    
42.     answer->x = MAX_Y(a,b);
    
43.     answer->y = ANSWER(a,b,c,answer->x);
    
44. 
    
45.     return 1;
    
46. }
    
47. 
    
48. // 计算顶点式
    
49. int vertex_type(double a,double b,double c,pVERTEX_TYPE ver){
    
50.     NOT_ZERO(a);
    
51. 
    
52.     double a1,h1,k1;
    
53.     POINT p1;
    
54. 
    
55.     vertex(a,b,c,&p1);
    
56.     h1 = p1.x;
    
57.     k1 = ANSWER(a,b,c,h1);
    
58.     a1 = (ANSWER(a,b,c,0) - k1)/(SQUARE(h1));
    
59. 
    
60.     ver->a = a1;
    
61.     ver->k = k1;
    
62.     ver->h = h1;
    
63. 
    
64.     return 1;
    
65. }
    
66. 
    
67. int main()
    
68. {
    
69.     // 输入一元二次方程的一般式系数
    
70.     double a=1;
    
71.     double b=-4;
    
72.     double c=3;
    
73. 
    
74.     ANSWER_X answer;
    
75.     POINT point;
    
76.     VERTEX_TYPE ver;
    
77. 
    
78.     if(solute(a,b,c,&answer)){
    
79.         printf("The quadratic answer is :\n");
    
80.         printf("\tx1 = %.3lf\n\tx2 = %.3lf\n",answer.x1,answer.x2);
    
81.     }
    
82. 
    
83.     if(vertex(a,b,c,&point)){
    
84.         printf("The vertex-point is :\n");
    
85.         printf("\t( %.3lf , %.3lf )\n",point.x,point.y);
    
86.     }
    
87. 
    
88.     if(vertex_type(a,b,c,&ver)){
    
89.         printf("The vertex-type is :\n");
    
90.         printf("\ty = %.3lf * (x - (%.3lf))^2 + (%.3lf)\n",ver.a,ver.h,ver.k);
    
91.     }
    
92. 
    
93. 
    
94.     return 0;
    
95. }

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