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

Question

14.8k 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 | 14.8k 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