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;
}