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

Question

18.8k 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 | 18.8k 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;
}