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

Question

7.8k 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 | 7.8k 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