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