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

Question

19.4k 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 | 19.4k 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