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

Question

8.6k 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 | 8.6k views

56 Answers

Page:

« prev
1
2
3
4
5
6
next »

Headshake · Answer 1 · 2017-11-14 15:44:31

Hidden content!
#include <stdio.h>
**  **     ***** *
int main()
{
* *  *  * ** *     **   ** **** * **  *** ** *** * *** **
 * * * ** * * * *  *   *   *  *** **** * * %f  **      * ** *** ** * ****** * 
**  *   **  * **    * *  * * * = (b*b-4*a*c);
  *    ***  *  *   * *  * = (-b + sqrt(D))/(2*a);
* *** * *  ** **** * ***  *    * = (-b - sqrt(D))/(2*a);
** * * * *  *  ** ** * **  **     = -b/(2*a);
 ** **    * * ** ** * **     *** **  =sqrt(-D)/(2*a);
** * **  *** *** * * *       *** ***  **  
*    * ***   * * ***** *   ***
  *   *  ** ** ** * ****  *  ** * *  ********  *  ****** *      of %.2fx^2 + %.2fx + %.2f = 0 are real and  ********    * *
**** ***   *  **   ***  *       *   ** ** *     *** *   ***  *** ***  *    *  ** = %.2f\nx2 = %.2f",x1,x2);
** *    ** **  *    *  ****

* * *** * *    * ** ***  **  **  * if(D==0)
  *  ***  * *        ** **    
 *  *  ** *******  *  *  ** *** * *  * *    **     * * *  **    ** *  ** of %.2fx^2 + %.2fx + %.2f = 0 are real and same\n",a,b,c);
 * *   ***** **   *    *     **    *    *** *   **    * * * **  ** = x2 = %.2f",x1);
* **  **   ***  * ** * *** *
 **  *****  *    * ** *        
* *  *** *    *  *  *  *   *
* *** * **     **  * **    **** ** ******       * *   ** * ** *   **  * of %.2fx^2 + %.2fx + %.2f = 0 are complex and  ********* *      
 *  **   *   *  *  **  *  * *  ** *   * *      *    ******** =  * **   ***  ***   * *  ***
  **   **** * * * *  ** ** ***** *    **   ***   * ** *  *  *  =  *   *  ** * *** *  **   *  * 
  * *** *  *****    * *   *** 
***    * * * *   ** *   0;
}

answered Nov 14, 2017 by Headshake (-281 points)

Headshake · Answer 2 · 2017-11-14 15:42:56

Hidden content!
#include <stdio.h>
** ** **     ** *
int main()
{
      ***  *  **   *** * * *    * *****     *   * **** ***
**  *   *   ****   *   * **  *    ** **  %f ** *     ** *****   *   * *     
 *****   ****    **  *    = (b*b-4*a*c);
**   ***    ** **  ***** * * = (-b + sqrt(D))/(2*a);
     *  *   *    *  ****  *** = (-b - sqrt(D))/(2*a);
** * * * * * ****        *  * **  * = -b/(2*a);
***** **  *** *** * ** *   *     *  *   =sqrt(-D)/(2*a);
 **** *  *** ***    *** **** *****  
*** * ***  **  *    * ***    
  *****  *  * * *** * * *  ** *** ***   ***  ** *  ** ** *   ****    * *   of %.2f x^2 + %.2f x + %.2f = 0 are real and ***  *  *           *
   * ***  ** *  **      *** *  **   *  **    *  ***  **** **  = %.2f\nx2 = %.2f",x1,x2);
 ** ** *  **** ** ** *   * * 

 ** *****  ***** * * ** *  *  * if(D==0)
** *  **           *******   
 * **   *   * *  **  * ***** *  * ** * *   *****  *  *       ****  ***  of %.2fx^2 + %.2fx + %.2f = 0 are real and same\n",a,b,c);
 * ** ***  ** ***   ** **  * ** **   ****** *** * ***    *  *** * = x2 = %.2f",x1);
   * * * *  * **  ** **    
    * *  * *** *  ****  ****  *
* * *** * * * * ** *   
 *    * * * *    * ***    ** ***** ** ** * ***    *  * * * **** * of %.2fx^2 + %.2fx + %.2f = 0 are complex and  *        *  ** * ***
* ********    ***  ***   ** * **   ** * ** ** * * * * ****   ** ** = **  ******** ****** ***   
 *** * *******   * *    * *  **** ** *    **   *    *****   **   *** =  * **  **  * *  **     **  * * *
  *** ** **  *  * *** ****
**  *    *   * ***  * ****   *     0;
}

answered Nov 14, 2017 by Headshake (-281 points)

watty1998871108 · Answer 3 · 2017-11-14 00:38:04

Hidden content!
#include <stdio.h>
#include <stdlib.h>

int main()

{
 * * ** *  * ** ** * **   *** * a,b,c,x1,x2,D=0;
    ** * ** ***  *       ** 
**  ** ** * **     * ****    * ****** **     %f ***** * * *  *** ***  *  **** 
***  *  ***   *    **** *
  ** ****** *  *   * * *  ***  
  *   **  * * *  * *  * *** **      *** + sqrt(D))/(2*a);
* * * **  * *****  ** *   *  *  - sqrt(D))/(2*a);
   * *    **      **  * *   *
*** ***   *  **  *** *  * * **     ***  *
 * * ** ** *    *   *  * *** * 
**  * * ** *  ***  ****  *  * * *  * * * ** ** **      *** *  of %.2fx^2+%.2fx+%.2f=0 are complex and **   ** **   ** *   *  ***   ** 
   *****     ******   **** ** 
 * **  *   *    *    ***** * 
     ** * *      *  *** if(D==0)
     * ** *****  * * **
* * * *     ***  **  * * *   ** **   *   * * * *** ** *****  ** **** ** of %.2fx^2+%.2fx+%.2f=0 are real and same\nx1=x2=%.2f",a,b,c,x1);
* * * * *  *************    **
* ** *   *  *** **  *   
* **** ** * **** * *   
**** ** *** ** ***  *** **
*  *  * **** ****  * **  * ******   ******** * * * * *   *  *  * ** * of %.2fx^2+%.2fx+%.2f=0 are real and    **  *** **   * ***  *    ***** *
*   *   * * *  * **** **   
*  ** * * ***  *** *  *******
*********   * **********
**  ***  * *  ** ** * * * * ** 0;
}

answered Nov 14, 2017 by watty1998871108 (-127 points)

benson2 · Answer 4 · 2017-11-13 21:17:31

prog.c: In function 'main':
prog.c:6:5: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
     scanf("%f%f%f",&a,&b,&c);
     ^~~~~
prog.c:6:5: warning: incompatible implicit declaration of built-in function 'scanf'
prog.c:6:5: note: include '<stdio.h>' or provide a declaration of 'scanf'
prog.c:12:9: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
         printf("Roots of %.2fx^2 + %.2fx + %.2f = 0 are real and same\n",a,b,c);
         ^~~~~~
prog.c:12:9: warning: incompatible implicit declaration of built-in function 'printf'
prog.c:12:9: 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 complex and different\n",a,b,c);
         ^~~~~~
prog.c:17:9: note: include '<stdio.h>' or provide a declaration of 'printf'
prog.c:23:9: warning: incompatible implicit declaration of built-in function 'printf'
         printf("Roots of %.2fx^2 + %.2fx + %.2f = 0 are complex and different\n",a,b,c);
         ^~~~~~
prog.c:23:9: note: include '<stdio.h>' or provide a declaration of 'printf'

benson2 · Answer 5 · 2017-11-13 21:16:23

Hidden content!
*     * **   *  ***   
int main()
{
  *** * ***  * ***** * *  * *  a,b,c,D;
*    ***  * *      ***  **      x1,x2,r,i;
  ****** * ** *  * *** **  **** *******  * **   * * **   ** * ** ** * 
  *  ** * *** ***      *  ***     *  ***  * * 
   * * ****  *** **** ***  * *  * ** ** ****
* ** **** * **      ** ** * **      **  *
* **** * * *    **  **    *    
 ** ****   ***   **** *     *    
**   *         *********  ***  *** * ** **** *** **  *  * ***  ***** of %.2fx^2 + %.2fx + %.2f = 0 are real and same\n",a,b,c);
* * ** * *   *  *  ** **  **** ***  ** **  ***** ** *  *  **** **  = x2 = %.2f",x1);
      *****  *  ** **   *  
   *  * *    **     *   ** **** if(D>0)
*  **     *  * *    *** ** *  
   ***********   **  * *  *****         *   * ***   *** *** * ***    * of %.2fx^2 + %.2fx + %.2f = 0 are complex and ** *****   *****  * 
 *** *   ***     * ** ** ****      ***  **  *     * * * * * ** = %.2f\n",x1);
    * ****   *  *  ****  **  * * **  **   * *** **  *****  ** ****** = %.2f",x2);
  * ** * * ****  *** *** *  ***
*  *****  ** * ***** * ** * ***  if(D<0)
 ****   ** * *   ** ** *  * * 
* **  * ** * ** *  *    *** *  * * ** **   ** ** *  ****  ****   ***   * of %.2fx^2 + %.2fx + %.2f = 0 are complex and different\n",a,b,c);
* ** *** *     ** ** ** *  * ****  ** ***    ** * ** -b/(2*a);
  *   **  **   * *       *   *****  **    * **  * *  ** **   ******  *  
****  *   ** * *    *   *  *  * * ** * * * *  * *** * *   = %.2f+%.2fi\n",r,i);
  ******   *  *****  *    **  ***  *   *    * *****     *  *   *    ** = %.2f-%.2fi",r,i);
**  * * * ** *** *   ** **** * *
}

answered Nov 13, 2017 by benson2 (-329 points)

LinJingYao · Answer 6 · 2017-11-13 08:50:47

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

answered Nov 13, 2017 by LinJingYao (-498 points)

HuangWg · Answer 7 · 2017-11-12 22:05:16

Hidden content!
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main()
{
*  *  *    * *  ** * * ***** ** a,b,c,d,x1,x2;
** ***  ***   *   **  **   *   ***** **    ****   * *    **   ** ** ****
  *      *      ***    * *  ****
*** * * *** **  *** *  *   = (-b + sqrt(d))/(2*a);
* ****   *   * *    ***** **  *  = (-b - sqrt(d))/(2*a);
****** * **   **   * *  * *   ** * * ** *
*  * ** *  *   ***   **  **** *****  ******   ** *  ***  **** * * *      of %.2fx^2 + %.2fx + %.2f = 0 are real and different\n",a,b,c);
   * *******      *   *  * * ***** ** *  *    **  **** * *  * ****    *  *   ** *  ***  *    * ** **      *** *  *** * **   ** * *******  ****    **  **  ****    ** ***   * *** *  **  ** *   * *  **   * *  ****  *  * ** * * *   ** * ** = %.2f\n",x1);
  *  * ** **  *  **  *    * *  **  **  *  ** ******   ****    ***  **  * *  ***   **   * * * *  **   *  *  * * * * *        **   **    ***   **  *** *  *  ***  **   * * ***  **      *  **  * *******  * * * **     * ** **** *  ** *  = %.2f",x2);}
* *  *  ****  * *** *  * if(d==0)
*  **   *** ******* **  * *  * *** * ***  *****  **  
 * *     *** *  ***  **  **  *  *   *   **  *  *  ****  *  ********* ****  ** * ******   ***** of %.2fx^2 + %.2fx + %.2f = 0 are real and same\n",a,b,c);
**  *  **  *** *  *** * * ** **         *    *** *   ***  **  *  * * * * *    ** * ****   ** * **    *** ** *   *   * *   * * ***  *         *** *   *  = x2 = %.2f",x1);}
***    * *  *****  *   * * *** **
**   ***    **    ** **  ***   * * * **  ** ** *   ** *** ***     *  * *   of %.2fx^2 + %.2fx + %.2f = 0 are complex and different\n",a,b,c);
**   * *   ** *   *       * ******  * *  *  * ** *  * *   ***  = ** *    **     * *******   *  *
 *      *  *  ** * *  *  ** * ** **** ** ***** * * * * *  * ** ** = *****  ****  *** * ** * 
    *  ****  ** *    *  ** ** 0;
}

answered Nov 12, 2017 by HuangWg (-108 points)

Tedtsen · Answer 8 · 2017-11-12 16:56:08

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

int main()

{
* * **      *** *  *  *    ***  ** *** *   * * **** 
      * ***  **    ***  *  ***  *  * **  * %f * *  * **    ** *   ****   *   *

    ** ***** ****  ******** *
   *  **  *     ***** * * ** ***   + sqrt(D))/(2*a);
   **  * *****  * * **    **   -     * *** * 
 *   ***   *  * * *** * **   **  ***  * * *
* ***   *** **  ** **  *    ** * * *  *

  *** ***   * ** ** *****  (D==0)
     ***  **  **** ****   *
 *** *** **** *   ****  * *    *  * *  *  **   ***** *** ***     ** *  of %.2fx^2 + %.2fx + %.2f = 0 are real and same\nx1 = x2 = *   ** * *** *** *
       * * *  **** *** * ** 
*****  **   * *   ** * *******   if (D>0)
****** **  **    ********
* ***  * *    **** *    * * ******  *  *   *   **  ** ***  *     **** ***  ** of %.2fx^2 + %.2fx + %.2f = 0 are real and different\nx1 = %.2f\nx2 = **  **     * ** 
** **    *    *   *  *  ** *** 
* ** *** **   *   * ** **  **  
 *   ** ** *    ** **   * *   *   
****  ** * *  *** *** * *  *******    ********  *******  * *** *  *   *  *  of %.2fx^2 + %.2fx + %.2f = 0 are complex and different\nx1 = %.2f+%.2fi\nx2 =   *** * * ***** **  ** * *** *** *   
*** ** **  **    *    ** **  ** 

 * **  ******  *  *****  0;

}

answered Nov 12, 2017 by Tedtsen (-249 points)

~~~~~~ · Answer 9 · 2017-11-12 12:37:20

Hidden content!
#include * **   ***  * 
#include   * **** ****  *
int main(void)
{
float a,b,c, D, x1, x2,i;
*    ****  * *   **  *    *   *** *  *  %f  **   ** &a, &b, &c);
**  *** *** * * * **    * *    ** * 
*     **** **  ** *  * **   (D>0)
**     ** *** * ** * * *    
  **  **  *    * *  *      **    * ** ** *    *   * *   ** *****  
  *    ** **** *    * *   * * *  *  *  * *  *   *  *******  **** ***    

   * *   * ***   ** *  * *   ***   ***  *   ***   **** * *** *   *  * **** ***** of %.2fx^2 + %.2fx + %.2f = 0 are real and     **** *** = %.2f\nx2 = * *** *   *  **     *
**** *** **   *  * * *  *   
*        *   * **  *  *  ** *** if (D==0)
**    *     *****  * *  ** 
***    ***     *  **  ** * * * ***  **  ****   * * * *
  **  *   * **    ***     *   ** * *   * *  * ** **  *   ** *  ***    of %.2fx^2 + %.2fx + %.2f = 0 are real and same\nx1 = x2 =  ***  * ***    
* ***** *   ***    ** *   *  
  *** * * *  ** **   *   **  *  
 *   **  **     **** *    *
 * *** **       *** ***  *    x1=x2 = -b/(2*a);
   * *  ***   ** ** **   ** * * * * **   ***         * 
* *****    ** ** **  *  * **   * *** *  * ****   ***  *  ***  *** ** of %.2fx^2 + %.2fx + %.2f = 0 are complex and  *** * *  =   *  ** * = **    **** * ***  **  x2,i);
     *  * ***  * * ***



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

answered Nov 12, 2017 by ~~~~~~ (-304 points)
edited Dec 7, 2017 by ~~~~~~

112233 · Answer 10 · 2017-11-09 18:43:53

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

int main()
{
** * *   * *  ** *  ** ** **  a, b, c, *   *   * 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 (determinant > 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)

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

Please log in or register to add a comment.

56 Answers

Please log in or register to add a comment.

Please log in or register to add a comment.

Please log in or register to add a comment.

Please log in or register to add a comment.

Please log in or register to add a comment.

Please log in or register to add a comment.

Please log in or register to add a comment.

Please log in or register to add a comment.

Please log in or register to add a comment.

Please log in or register to add a comment.

No related questions found