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

Question

2.4k 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 | 2.4k 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;
}