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

Question

5.3k 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 | 5.3k 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;
}