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

Question

13.3k 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 | 13.3k 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