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

Question

18.2k 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 | 18.2k views

56 Answers

Page:

« prev
1
2
3
4
5
6
next »

112233 · Answer 1 · 2017-11-09 17:27:38

Hidden content!
#include * * *   ** * 
#include *     * * *  ** 

int main()
{
  *  ****** ****   *  * ** * a, b, c, determinant, 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   ***  *** > 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)

112233 · Answer 2 · 2017-11-09 17:17:35

Hidden content!
#include   ****  **   
#include  *        *  *

int main()
{
***    *  *   ***** ***  ** **   a, b, c, determinant, x1,x2, realPart, ** *  * **


*    ** * * **    * * **    **    * ***** ** %lf    ** **   *   &b, &c);


***  * *   *  ***  ***  **** *****   = b*b-4*a*c;

**** ** ******   *** ** **   *  condition for real and different roots
 *  * *** **  * *   * *  (determinant > 0)
*   *** *   * *  *  ** ****  
* *     *** *** * * * *     sqrt() function returns square root
   ****  * * *           *  ** ***  * ** * ** *  = ****** ****  *  *
  *** *  ****  *** ** * * * ***  *** *   *    **   *****  *** = * ****   * *  

* ****      * **    *****       * ** *   **** ****  **  ***** * ** of %.2fx^2 + %.2fx + %.2f = 0 are real and ** *  ** **  *** * * *
  *    *        * **  **   *****    *    *** * * **   * *   *  * ****  ** ** =  **   **  x1);
 **** **  ****** * *   * ** **** ** **** *    * ***    *  ****  **** =  ** *  *  ** x2);
 **  ** *    ****    *  * * *  *

*  *** ***  *  ** * ** **  ******** * * for real and equal roots
 *  * *    *  *   *  **  ** ** if (determinant == 0)
****  * ******  ***  * ** **
 **  *    * *  * **  *** ** **  ** *    * ** ** * * * * *  **  = x2 = -b/(2*a);
    *****  * ** **  **  *      ** ******  *****     ** *  * *  *****  * * of %.2fx^2 + %.2fx + %.2f = 0 are real and **  *** **  a,b,c);
** ***** * *  ****** ** *  * * **  * ***** *****    *  *   ** *   * = x2 = ***       x1);
        * ***  *   * ** * ** 

    ** *   *** *    **  *   * 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)

garrylin2 · Answer 3 · 2017-11-02 19:54:55

Hidden content!
 *  **      **** *   ***
*  **   * *  ** * **  
int main(void)
{
   * **   **  **  ** **  *  **   a,b,c,d;
  *  ** * ***    **** **   *  **   %f  * **   * **** **  *   *  ******   
 **    * * ***   **   ****** ** * *** *
** *  **   ** * *    * *  ** ** *   *  **
   *** *** *   ***   *  * * *****     *   **   *  **** **    ** * * *  of %.2fx^2 + %.2fx + %.2f = 0 are real and  * * **  = %.2f\nx2 = ***  * * *****   *** + * ** *    ** - *  *  * **
**** * *   *** * * ***   ** 
 *  ** * * *   * ** ***   ** (d==0){
* *  * ***  * ***** *    ** * **  ** ***  * ** * *   ******* **  **  *    *   of %.2fx^2 + %.2fx + %.2f = 0 are real and same\nx1 = x2 =   ***  *  *    * *  ** +    * * *
 ** * *   ** * * *****   ** * **
  *  *  ** ***  *  ******  (d<0) {
  * **  * *  ** *  **   **** * ***           ** **  * ***    *****  * of %.2fx^2 + %.2fx + %.2f = 0 are complex and    *   *  = *  ****  = * ****** ****  *** * **** ****  * ****   * **
 *****  **** *     * * **     *
}

answered Nov 2, 2017 by garrylin2 (-204 points)

garrylin2 · Answer 4 · 2017-11-02 19:53:31

Hidden content!
    **  *    ***
* **  * * * ** * ****
int main(void)
{
  * **** * *  ***    * *** **     a,b,c,d;
*   **  *  * **  **   ** *** * **    **** %f *  ******* *  **** ** **  *   *****
***   ** *** **  ** * *    * ***   *
*     *  * *** ** ***** * ** * (d>0){
 *** ****** **   * **  *  *** * *  * *** *  * *  *      ** *****  *  * of %.2fx^2 + %.2fx + %.2f = 0 are real and ********** = %.2f\nx2 =  **  * **       ** + **      *  - *  ** *  ***
*  * **      **   *   * ** *** 
 ***  ****  *  ** * *    **   ** * (d==0){
  **    ****  *  *   ** *         * *** *  * **  *****   *    *   **  * * * of %.2fx^2 + %.2fx + %.2f = 0 are real and same\nx1 = x2 = ** ***  * *****  + *****  *  **
  * ***  *  **         
***  * ** *** **** *  *      *  {
*  * * *  ****   *** ****    **  **** *  *  ****  *  * *** * *****  *** of %.2fx^2 + %.2fx + %.2f = 0 are complex and  **   *   =  *     = *  *  **    * *****  ***** *       ***  ****  **  ** 
 *  * *  **     *** ** *   *
}

answered Nov 2, 2017 by garrylin2 (-204 points)

rick · Answer 5 · 2017-11-02 19:34:07

prog.c: In function 'main':
prog.c:5:5: warning: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
     scanf("%f %f %f",&a,&b,&c);
     ^~~~~
prog.c:5:5: warning: incompatible implicit declaration of built-in function 'scanf'
prog.c:5:5: note: include '<stdio.h>' or provide a declaration of 'scanf'
prog.c:13:9: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
         printf("Roots of %.2fx^2 + %.2fx + %.2f = 0 are real and different\nx1=%.2f\nx2=%.2f\n",a,b,c,x1,x2);
         ^~~~~~
prog.c:13:9: warning: incompatible implicit declaration of built-in function 'printf'
prog.c:13:9: 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 real and same\nx1 = x2 = %.2f",a,b,c,x1);
         ^~~~~~
prog.c:17:9: note: include '<stdio.h>' or provide a declaration of 'printf'
prog.c:21:9: warning: incompatible implicit declaration of built-in function 'printf'
         printf("Roots of %.2fx^2 + %.2fx + %.2f = 0 are complex and different\nx1 = %.2f+%.2fi\nx2 = %.2f-%.2fi",a,b,c,x3,x4,x3,x4);
         ^~~~~~
prog.c:21:9: note: include '<stdio.h>' or provide a declaration of 'printf'

rick · Answer 6 · 2017-11-02 19:28:09

Hidden content!
#include<stdio.h>
#include<math.h>
int main()
{
*       *****  *  ** ****    a,b,c,d,x1,x2,x3,x4;
**      *   ** * *  * *** *    *** * * * %f **  ** *** *  ** *    ** *  
  * * *    *  ** * **  ****    *
*****  **** ***    ****  ** *    ****  
****    * ** **    **  ** *     **  * * * 
**** ***   ***     *  * *** **
 *** ** *** * ** * **    *** *   ***
 * *       ** ** ***  **  * * * ** * *  ** * *  ** *
   ***    * * **   * 
 *** ** * *   ** *  * **** ** *** * * * *** *   *  **  * *  *      *****  of %.2fx^2 + %.2fx + %.2f = 0 are real and ** ** *     * ** **         ******  * 
****      ***  *   * *****   *  *
***  *  * ** *  *** *   ** **** ** *  ** **  *  *   *** ****
***   ***** *** *  **  * * * * 
*   *  * *** *  **  ** * **  *  * ***  * * *  *   * * *  ** * *** *   **   ***** of %.2fx^2 + %.2fx + %.2f = 0 are real and same\nx1 = x2 = %.2f",a,b,c,x1);
********    * *  *   ***** **
 * *      * * ******* * *    * *   ** ***  *  *    *  **  * **** 
*  ** *     *   *   *   *  
 **** ****     **  ** ** *  ****    * ** ** **  * * **  *****        ** of %.2fx^2 + %.2fx + %.2f = 0 are complex and different\nx1 = %.2f + %.2fi\nx2 = %.2f -   *****   * ** ****   
   * **  *   **** * **   * *
*   ** *     *  *  *  ** *    ** 0;
}