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

Question

18.6k 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 | 18.6k 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;
}