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

Question

2.3k 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 | 2.3k 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