10-26 Exercise 3: Find roots of a quadratic equation

Question

17.5k views

Write a program to find roots of a quadratic equation

A quadratic equation is a second order equation having a single variable. Any quadratic equation can be represented as where a, b and c are constants ( a can't be 0) and x is unknown variable.

寫一個找二次方程的求根程式

For Example

is a quadratic equation where a, b and c are 2, 5 and 3 respectively.

To calculate the roots of quadratic equation we can use below formula. There are two solutions of a quadratic equation.

使用下列公式:

x = (-b + sqrt(D))/(2*a)
x = (-b - sqrt(D))/(2*a)

where, D = (b*b-4*a*c) is Discriminant (判別式), which differentiate the nature of the roots of quadratic equation.

For the complex result (複數根):

realPart = -b/(2*a);
imaginaryPart =sqrt(-D)/(2*a);

Note: We have used sqrt() function to find square root which is in math.h library.

Example input 1:

1 2 1

Example output 1:

Roots of 1.00x^2 + 2.00x + 1.00 = 0 are real and same
x1 = x2 = -1.00

Example input 2:

1 -3 2

Example output 2:

Roots of 1.00x^2 + -3.00x + 2.00 = 0 are real and different
x1 = 2.00
x2 = 1.00

Example input 3:

1 2 2

Example output 3:

Roots of 1.00x^2 + 2.00x + 2.00 = 0 are complex and different
x1 = -1.00+1.00i
x2 = -1.00-1.00i

[Exercise] Coding (C) - asked Oct 26, 2017 in Chapter 5: Selection Statements by semicolon (5.2k points)
ID: 28934 - Available when: 2017-10-26 18:00 - Due to: Unlimited
reopened Oct 26, 2017 by thopd | 17.5k views

56 Answers

Page:

« prev
1
2
3
4
5
6
next »

112233 · Answer 1 · 2017-11-09 17:27:38

Hidden content!
#include  *** ** * * **
#include *** **  *** ****

int main()
{
***    *   *  *   ** *** * *   *** a, b, c, determinant, x1,x2, realPart, *  **    


** *     ** **      *  **  * *** **** *** * %lf *  * ****** * &b, &c);


* *   *** * *  *   ***** ***** * *  = b*b-4*a*c;

    **  *   * ** *  ***** **    condition for real and different roots


  ** ****  *  *      **** **** for real and equal roots
**** * ** ******  ***  **** * **  (determinant == 0)
 * * * * ** * *     ** * *   
** ***  * ***  ** *  **  **** *** ***    *  * * **** *   ** = x2 = -b/(2*a);
* **   ****       * **  **** *  ** ** *    ** *** **   *   ****    ** of %.2fx^2 + %.2fx + %.2f = 0 are real and   * * **   a,b,c);
  *  ** ** *     *  ** ****  * *****  **** ** * ******   *  = x2 =   ** **   x1);
   **** * *   ** *    ** *   *

   * * ** **** *  ** **     *        if  ****** > 0)
*  **  ***** **     **    
*  *   *  ** *       * ** *   sqrt() function returns square root
**   *   ***** ***  **** ** *     *    * *  * *   ** = *  *     **  * *   
* * *  ** ** *  **   **  * ** ** *    * ****  **** *   * * *  =  ***  * **  **  ***

  * *   *   ** * **  ***  *** * *  *** *  ** * *** *   *   **   *  *  *   * of %.2fx^2 + %.2fx + %.2f = 0 are real and   **      **  *****
  *  *   ***  **   *   *** *      * *  * *** ** **** ***    *** = * *     x1);
* ***  *   **  * ****   ** * *  ******  * *   ** *  *   *** *  **** *   =   **  **  * x2);
 *  ******    *   *    **  ***  if roots are not real
  *  **   * *  ***  **     *
** *** * *  * *    * * *   
 **  *   ** **   * ****   *  ****  ******  *   * * ** * = -b/(2*a);
*  ** ** * **       * **  ** **** ****  **   ** * **  ** *** **  = ***  * * * *   * 
***  *** **  ** * ******* ** *    *  * **  *    ***  *    ** *  of %.2fx^2 + %.2fx + %.2f = 0 are complex and * **  *     *  a,b,c);
  ** * ***  **    ** ***   *   **     **  **   **  *** **  ** *****  =  *** *  *  *****  * realPart, **** *****
 * *  ** ***      *  *** * *  *  * *      * ** *** **     * * = * * *  * *  *  *  realPart, * **** * *** 
  ** *   **** *****   **  *  

**     *   *   * *  ** *  0;
}

answered Nov 9, 2017 by 112233 (-167 points)

112233 · Answer 2 · 2017-11-09 17:17:35

Hidden content!
#include * * ****   ** **
#include  * *       ** 

int main()
{
* ** *******      *********   ***  a, b, c, determinant, x1,x2, realPart, ******  


   **   **** **    ***    * *   * ** *  %lf ** ** *    *  * ** &b, &c);


  ** * ***  ****    *** ** **** *  * = b*b-4*a*c;

**  *   * * ** *** **** * condition for real and different roots
  *  * * * ***   *  ** ** * (determinant > 0)
 * ****** * * ********
  **** *****  * **    *   *     sqrt() function returns square root
      *  * * ***  *  **          * * * * ***  *    =  *  * * *  ****   ****
 *   **   * ** **  * * * ** * *** *** **    * **    *  = ** * ** **  **** 

 ****** *  *    *  *  *  *  ***** ***    * * * * ***  ** ** *  of %.2fx^2 + %.2fx + %.2f = 0 are real and    * ** * * **  **  ***
 * *****   **  **    ***  **  *******  **   *  ****   *  *** **   * **   *      =   **    **  x1);
***  *  *  ***   *** ** *   *   **** **   ** *    **** *  * *  * =  ** *  *** ** x2);
  *** *   **  *   **** * * ****

     ***      ** * * *  * ***** for real and equal roots
 *  *   * ***    ** ****      if (determinant == 0)
 ** ***   *  ** ** ** *  ****
*** * **   *****  * * ** **  * *  ********   * * ***  * = x2 = -b/(2*a);
 * * * **  * ** ** *    ****** *   * **  *  ** * ** ***  *  **   *   *   * of %.2fx^2 + %.2fx + %.2f = 0 are real and   *****  a,b,c);
***      **   *     ***    *    **  * *     ****   * ** **  ** *** ** = x2 =      ***** x1);
 **  *  **   ***   * ** * *  

  **  **       *  * *  *  * if roots are not real
* * ****  * * *  **  *  * *   ***
 * * **** * *  *  **  **  
****   * *** ****** **   **   ***  *   *     * ** **  ** = -b/(2*a);
   *  *       ***  * * * **   ***   ** *  ***** * **  ****** = *****    *** ****
  *        *  **   ** * ******  **      ****   * *** *   *** ** ** of %.2fx^2 + %.2fx + %.2f = 0 are complex and * *   ** **  * a,b,c);
 ***    * ****  *  * ***      ** *** *  *  * ***  * ****   **  * * = * **  ********    realPart,  *  * ** 
* ***  ***   * ** * *    ****  * *  ***  **  ***  * **  * **    *** * =  * ** **  *** realPart,   * * **    **
***    * ** * * ****   *  

 ***  *   ****  *  ***  * *     0;
}

answered Nov 9, 2017 by 112233 (-167 points)

garrylin2 · Answer 3 · 2017-11-02 19:54:55

Hidden content!
   *  * ****   * * *** *
 *** *****  * *** ** 
int main(void)
{
 **  * * *** * **  * ******* **  *** a,b,c,d;
** * *  **** *  *  *   *  ** *  %f  ****** ** *  ***** *    *  **  *
 ** * ****  **** * * * *  ** ****   *
  *   * *  **** ***  ***   ***     ****
  **  *  * *  * *** **** ******    ** * ** * * **     *  *   of %.2fx^2 + %.2fx + %.2f = 0 are real and *** *  = %.2f\nx2 =   ***   *  ** * + **  ** * - ** *  * *  
 * * ** ** ****** *   *  *
 * **  * *  ***   * *** **    (d==0){
 * *** *  *  * *******    **  ** *   ** ** *       * ****** of %.2fx^2 + %.2fx + %.2f = 0 are real and same\nx1 = x2 =  * *** *** * * *** + *  *  ** **
**  *  ***  *     *** **** * * 
*  ** **** *** **** * * *   ** *** (d<0) {
 *  *   * ***  *    * ** **  *    *** *       **** *      *      *** ***   of %.2fx^2 + %.2fx + %.2f = 0 are complex and   * * **  =  *  **  =  *   ****** * *    ** * * ** *    *** *  *  ** *** 
   * * ****  *   **** *   
}

answered Nov 2, 2017 by garrylin2 (-204 points)

garrylin2 · Answer 4 · 2017-11-02 19:53:31

Hidden content!
** **** * ** ** * * * 
** ***** ********* ** *  *
int main(void)
{
   ***** *  ******** * * *  * a,b,c,d;
 * * * * *  ****   *** ***    **    ***  ** %f  *         * *  *****   *** *  
      *     *  * ** *  * **   ** *  **
   * *   * *      *  *****  (d>0){
*  *  *  ****   ***  *** *   * *  *** ****  *  * **** ***   of %.2fx^2 + %.2fx + %.2f = 0 are real and ***  *  = %.2f\nx2 = ************ ** +   * *    **** -   **   * * 
*   ** * **   *  ** *  *  * 
*      *  * **** *** **  * (d==0){
*    *    * *  ** * ***** *    *  *  *    * * ***  * **  ******  ** * of %.2fx^2 + %.2fx + %.2f = 0 are real and same\nx1 = x2 =   * ***  *  *   * +  *    ** *  
 *  ** * *        **  ** * *
*       ***   **         ****  {
 * * **  ** *   *  * * * ****   *   *** * **  * *   *      ***   ** of %.2fx^2 + %.2fx + %.2f = 0 are complex and * **** = * **** =  *  * ** **  **** * * *  * *      **  *  **** **
*** ** * ** *  ***    ***  **
}

answered Nov 2, 2017 by garrylin2 (-204 points)

rick · Answer 5 · 2017-11-02 19:34:07

prog.c: In function 'main':
prog.c:5:5: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
     scanf("%f %f %f",&a,&b,&c);
     ^~~~~
prog.c:5:5: warning: incompatible implicit declaration of built-in function 'scanf'
prog.c:5:5: note: include '<stdio.h>' or provide a declaration of 'scanf'
prog.c:13:9: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
         printf("Roots of %.2fx^2 + %.2fx + %.2f = 0 are real and different\nx1=%.2f\nx2=%.2f\n",a,b,c,x1,x2);
         ^~~~~~
prog.c:13:9: warning: incompatible implicit declaration of built-in function 'printf'
prog.c:13:9: note: include '<stdio.h>' or provide a declaration of 'printf'
prog.c:17:9: warning: incompatible implicit declaration of built-in function 'printf'
         printf("Roots of %.2fx^2 + %.2fx + %.2f = 0 are real and same\nx1 = x2 = %.2f",a,b,c,x1);
         ^~~~~~
prog.c:17:9: note: include '<stdio.h>' or provide a declaration of 'printf'
prog.c:21:9: warning: incompatible implicit declaration of built-in function 'printf'
         printf("Roots of %.2fx^2 + %.2fx + %.2f = 0 are complex and different\nx1 = %.2f+%.2fi\nx2 = %.2f-%.2fi",a,b,c,x3,x4,x3,x4);
         ^~~~~~
prog.c:21:9: note: include '<stdio.h>' or provide a declaration of 'printf'

rick · Answer 6 · 2017-11-02 19:28:09

Hidden content!
#include<stdio.h>
#include<math.h>
int main()
{
 *  * *** * *  * **  * * ** ***   a,b,c,d,x1,x2,x3,x4;
* ****  * **   *  ** ***      *     **** *** %f **   *  ****** *   * ***** *
* ** **   * ** ******* ** *  * **
**  **   ***     *   **   * ****** *  
* *** ****  ** **  ** *  * *      ** * ** *  ** 
* ** ***** * * ** *** * ** *** *  * *  
 * * *  **   **   * *****  * *   * ***  * *   
   *** ** ***  ****    * **  **  * * *   *  *  * *
       *   * * ** **  * * **
    *****   * **** *****   *** **  * * *  ** * *  ** *        *  ***  of %.2fx^2 + %.2fx + %.2f = 0 are real and   * * * *** ** *    * ** * ***   *    
 ***  *** **   *****  *   *  *
* *     *   ***  *  *  *  *    **  * ** **  *    ** 
*   ** **  ***  **  ** * ** 
 ** *** ** *** * *** * *   *  *   ** *** ****      * ****      * *  of %.2fx^2 + %.2fx + %.2f = 0 are real and same\nx1 = x2 = %.2f",a,b,c,x1);
* *  *  **    **   ** ***  *   *
** ******  *   *** **    ** **** *** ****      *********  
  **   * ** *   ** *  *   * 
**  *  *****  *******   *    *    *    *****  ** *  * ****      ** of %.2fx^2 + %.2fx + %.2f = 0 are complex and different\nx1 = %.2f + %.2fi\nx2 = %.2f - **   ** ** *  ***
         ** *  *** ** ***** *
* * ** * *** *       ***** * 0;
}