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

Question

14.8k 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 | 14.8k 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;
}