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

Question

13.3k 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 | 13.3k 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;
}