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

Question

9.1k 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 | 9.1k 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;
}